The .NET Framework gives us the Format method:
string s = string.Format("This {0} very {1}.", "is", "funny");
// s is now: "This is very funny."
I would like an "Unformat" function, something like:
object[] params = string.Unformat("This {0} very {1}.", "This is very funny.");
// params is now: ["is", "funny"]
I know something similar exists in the ANSI-C library (printf vs scanf).
The question: is there something similiar in C#?
Update: Capturing groups with regular expressions are not the solution I need. They are also one way. I'm looking for a system that can work both ways in a single format. It's OK to give up some functionality (like types and formatting info).
There's no such method, probably because of problems resolving ambiguities:
string.Unformat("This {0} very {1}.", "This is very very funny.")
// are the parameters equal to "is" and "very funny", or "is very" and "funny"?
Regular expression capturing groups are made for this problem; you may want to look into them.
Regex with grouping?
/This (.*?) very (.*?)./
If anyone's interested, I've just posted a scanf() replacement for .NET. If regular expressions don't quite cut it for you, my code follows the scanf() format string quite closely.
You can see and download the code I wrote at http://www.blackbeltcoder.com/Articles/strings/a-sscanf-replacement-for-net.
You could do string[] parts = string.Split(' '), and then extract by the index position parts[1] and parts [3] in your example.
Yep. These are called "regular expressions". The one that will do the thing is
This (?<M0>.+) very (?<M1>.+)\.
#mquander: Actualy, PHP solves it even different:
$s = "This is very very funny.";
$fmt = "This %s very %s.";
sscanf($s, $fmt, $one, $two);
echo "<div>one: [$one], two: [$two]</div>\n";
//echo's: "one: [is], two: [very]"
But maybe your regular expression remark can help me. I just need to rewrite "This {0} very {1}." to something like: new Regex(#"^This (.*) very (.*)\.$"). This should be done programmatical, so I can use one format string on the public class interface.
BTW: I've already have a parser to find the parameters: see the Named Format Redux blog entry by Phil Haack (and yes, I also want named paramters to work both ways).
I came across the same problem, i belive that there is a elegante solution using REGEX... but a came up with function in C# to "UnFormat" that works quite well. Sorry about the lack of comments.
/// <summary>
/// Unformats a string using the original formating string.
///
/// Tested Situations:
/// UnFormat("<nobr alt=\"1\">1<nobr>", "<nobr alt=\"{0}\">{0}<nobr>") : "1"
/// UnFormat("<b>2</b>", "<b>{0}</b>") : "2"
/// UnFormat("3<br/>", "{0}<br/>") : "3"
/// UnFormat("<br/>4", "<br/>{0}") : "4"
/// UnFormat("5", "") : "5"
/// UnFormat("<nobr>6<nobr>", "<nobr>{0}<nobr>") : "6"
/// UnFormat("<nobr>2009-10-02<nobr>", "<nobr>{0:yyyy-MM-dd}<nobr>") : "2009-10-02"
/// UnFormat("<nobr><nobr>", "<nobr>{0}<nobr>") : ""
/// UnFormat("bla", "<nobr>{0}<nobr>") : "bla"
/// </summary>
/// <param name="original"></param>
/// <param name="formatString"></param>
/// <returns>If an "unformat" is not possible the original string is returned.</returns>
private Dictionary<int,string> UnFormat(string original, string formatString)
{
Dictionary<int, string> returnList = new Dictionary<int, string>();
try{
int index = -1;
// Decomposes Format String
List<string> formatDecomposed = new List<string> (formatString.Split('{'));
for(int i = formatDecomposed.Count - 1; i >= 0; i--)
{
index = formatDecomposed[i].IndexOf('}') + 1;
if (index > 0 && (formatDecomposed[i].Length - index) > 0)
{
formatDecomposed.Insert(i + 1, formatDecomposed[i].Substring(index, formatDecomposed[i].Length - index));
formatDecomposed[i] = formatDecomposed[i].Substring(0, index);
}
else
//Finished
break;
}
// Finds and indexes format parameters
index = 0;
for (int i = 0; i < formatDecomposed.Count; i++)
{
if (formatDecomposed[i].IndexOf('}') < 0)
{
index += formatDecomposed[i].Length;
}
else
{
// Parameter Index
int parameterIndex;
if (formatDecomposed[i].IndexOf(':')< 0)
parameterIndex = Convert.ToInt16(formatDecomposed[i].Substring(0, formatDecomposed[i].IndexOf('}')));
else
parameterIndex = Convert.ToInt16(formatDecomposed[i].Substring(0, formatDecomposed[i].IndexOf(':')));
// Parameter Value
if (returnList.ContainsKey(parameterIndex) == false)
{
string parameterValue;
if (formatDecomposed.Count > i + 1)
if (original.Length > index)
parameterValue = original.Substring(index, original.IndexOf(formatDecomposed[i + 1], index) - index);
else
// Original String not valid
break;
else
parameterValue = original.Substring(index, original.Length - index);
returnList.Add(parameterIndex, parameterValue);
index += parameterValue.Length;
}
else
index += returnList[parameterIndex].Length;
}
}
// Fail Safe #1
if (returnList.Count == 0) returnList.Add(0, original);
}
catch
{
// Fail Safe #2
returnList = new Dictionary<int, string>();
returnList.Add(0, original);
}
return returnList;
}
I reference earlier reply, wrote a sample see following
string sampleinput = "FirstWord.22222";
Match match = Regex.Match(sampleinput, #"(\w+)\.(\d+)$", RegexOptions.IgnoreCase);
if(match.Success){
string totalmatchstring = match.Groups[0]; // FirstWord.22222
string firstpart = match.Groups[1]; // FirstWord`
string secondpart = match.Groups[2]; // 22222
}
Is there any way to format a string by name rather than position in C#?
In python, I can do something like this example (shamelessly stolen from here):
>>> print '%(language)s has %(#)03d quote types.' % \
{'language': "Python", "#": 2}
Python has 002 quote types.
Is there any way to do this in C#? Say for instance:
String.Format("{some_variable}: {some_other_variable}", ...);
Being able to do this using a variable name would be nice, but a dictionary is acceptable too.
There is no built-in method for handling this.
Here's one method
string myString = "{foo} is {bar} and {yadi} is {yada}".Inject(o);
Here's another
Status.Text = "{UserName} last logged in at {LastLoginDate}".FormatWith(user);
A third improved method partially based on the two above, from Phil Haack
Update: This is now built-in as of C# 6 (released in 2015).
String Interpolation
$"{some_variable}: {some_other_variable}"
I have an implementation I just posted to my blog here: http://haacked.com/archive/2009/01/04/fun-with-named-formats-string-parsing-and-edge-cases.aspx
It addresses some issues that these other implementations have with brace escaping. The post has details. It does the DataBinder.Eval thing too, but is still very fast.
Interpolated strings were added into C# 6.0 and Visual Basic 14
Both were introduced through new Roslyn compiler in Visual Studio 2015.
C# 6.0:
return "\{someVariable} and also \{someOtherVariable}" OR
return $"{someVariable} and also {someOtherVariable}"
source: what's new in C#6.0
VB 14:
return $"{someVariable} and also {someOtherVariable}"
source: what's new in VB 14
Noteworthy features (in Visual Studio 2015 IDE):
syntax coloring is supported - variables contained in strings are highlighted
refactoring is supported - when renaming, variables contained in strings get renamed, too
actually not only variable names, but expressions are supported - e.g. not only {index} works, but also {(index + 1).ToString().Trim()}
Enjoy! (& click "Send a Smile" in the VS)
You can also use anonymous types like this:
public string Format(string input, object p)
{
foreach (PropertyDescriptor prop in TypeDescriptor.GetProperties(p))
input = input.Replace("{" + prop.Name + "}", (prop.GetValue(p) ?? "(null)").ToString());
return input;
}
Of course it would require more code if you also want to parse formatting, but you can format a string using this function like:
Format("test {first} and {another}", new { first = "something", another = "something else" })
There doesn't appear to be a way to do this out of the box. Though, it looks feasible to implement your own IFormatProvider that links to an IDictionary for values.
var Stuff = new Dictionary<string, object> {
{ "language", "Python" },
{ "#", 2 }
};
var Formatter = new DictionaryFormatProvider();
// Interpret {0:x} where {0}=IDictionary and "x" is hash key
Console.WriteLine string.Format(Formatter, "{0:language} has {0:#} quote types", Stuff);
Outputs:
Python has 2 quote types
The caveat is that you can't mix FormatProviders, so the fancy text formatting can't be used at the same time.
The framework itself does not provide a way to do this, but you can take a look at this post by Scott Hanselman. Example usage:
Person p = new Person();
string foo = p.ToString("{Money:C} {LastName}, {ScottName} {BirthDate}");
Assert.AreEqual("$3.43 Hanselman, {ScottName} 1/22/1974 12:00:00 AM", foo);
This code by James Newton-King is similar and works with sub-properties and indexes,
string foo = "Top result for {Name} was {Results[0].Name}".FormatWith(student));
James's code relies on System.Web.UI.DataBinder to parse the string and requires referencing System.Web, which some people don't like to do in non-web applications.
EDIT: Oh and they work nicely with anonymous types, if you don't have an object with properties ready for it:
string name = ...;
DateTime date = ...;
string foo = "{Name} - {Birthday}".FormatWith(new { Name = name, Birthday = date });
See https://stackoverflow.com/questions/271398?page=2#358259
With the linked-to extension you can write this:
var str = "{foo} {bar} {baz}".Format(foo=>"foo", bar=>2, baz=>new object());
and you'll get "foo 2 System.Object".
I think the closest you'll get is an indexed format:
String.Format("{0} has {1} quote types.", "C#", "1");
There's also String.Replace(), if you're willing to do it in multiple steps and take it on faith that you won't find your 'variables' anywhere else in the string:
string MyString = "{language} has {n} quote types.";
MyString = MyString.Replace("{language}", "C#").Replace("{n}", "1");
Expanding this to use a List:
List<KeyValuePair<string, string>> replacements = GetFormatDictionary();
foreach (KeyValuePair<string, string> item in replacements)
{
MyString = MyString.Replace(item.Key, item.Value);
}
You could do that with a Dictionary<string, string> too by iterating it's .Keys collections, but by using a List<KeyValuePair<string, string>> we can take advantage of the List's .ForEach() method and condense it back to a one-liner:
replacements.ForEach(delegate(KeyValuePair<string,string>) item) { MyString = MyString.Replace(item.Key, item.Value);});
A lambda would be even simpler, but I'm still on .Net 2.0. Also note that the .Replace() performance isn't stellar when used iteratively, since strings in .Net are immutable. Also, this requires the MyString variable be defined in such a way that it's accessible to the delegate, so it's not perfect yet.
My open source library, Regextra, supports named formatting (amongst other things). It currently targets .NET 4.0+ and is available on NuGet. I also have an introductory blog post about it: Regextra: helping you reduce your (problems){2}.
The named formatting bit supports:
Basic formatting
Nested properties formatting
Dictionary formatting
Escaping of delimiters
Standard/Custom/IFormatProvider string formatting
Example:
var order = new
{
Description = "Widget",
OrderDate = DateTime.Now,
Details = new
{
UnitPrice = 1500
}
};
string template = "We just shipped your order of '{Description}', placed on {OrderDate:d}. Your {{credit}} card will be billed {Details.UnitPrice:C}.";
string result = Template.Format(template, order);
// or use the extension: template.FormatTemplate(order);
Result:
We just shipped your order of 'Widget', placed on 2/28/2014. Your {credit} card will be billed $1,500.00.
Check out the project's GitHub link (above) and wiki for other examples.
private static Regex s_NamedFormatRegex = new Regex(#"\{(?!\{)(?<key>[\w]+)(:(?<fmt>(\{\{|\}\}|[^\{\}])*)?)?\}", RegexOptions.Compiled);
public static StringBuilder AppendNamedFormat(this StringBuilder builder,IFormatProvider provider, string format, IDictionary<string, object> args)
{
if (builder == null) throw new ArgumentNullException("builder");
var str = s_NamedFormatRegex.Replace(format, (mt) => {
string key = mt.Groups["key"].Value;
string fmt = mt.Groups["fmt"].Value;
object value = null;
if (args.TryGetValue(key,out value)) {
return string.Format(provider, "{0:" + fmt + "}", value);
} else {
return mt.Value;
}
});
builder.Append(str);
return builder;
}
public static StringBuilder AppendNamedFormat(this StringBuilder builder, string format, IDictionary<string, object> args)
{
if (builder == null) throw new ArgumentNullException("builder");
return builder.AppendNamedFormat(null, format, args);
}
Example:
var builder = new StringBuilder();
builder.AppendNamedFormat(
#"你好,{Name},今天是{Date:yyyy/MM/dd}, 这是你第{LoginTimes}次登录，积分{Score:{{ 0.00 }}}",
new Dictionary<string, object>() {
{ "Name", "wayjet" },
{ "LoginTimes",18 },
{ "Score", 100.4 },
{ "Date",DateTime.Now }
});
Output:
你好,wayjet,今天是2011-05-04, 这是你第18次登录，积分{ 100.40 }
Check this one:
public static string StringFormat(string format, object source)
{
var matches = Regex.Matches(format, #"\{(.+?)\}");
List<string> keys = (from Match matche in matches select matche.Groups[1].Value).ToList();
return keys.Aggregate(
format,
(current, key) =>
{
int colonIndex = key.IndexOf(':');
return current.Replace(
"{" + key + "}",
colonIndex > 0
? DataBinder.Eval(source, key.Substring(0, colonIndex), "{0:" + key.Substring(colonIndex + 1) + "}")
: DataBinder.Eval(source, key).ToString());
});
}
Sample:
string format = "{foo} is a {bar} is a {baz} is a {qux:#.#} is a really big {fizzle}";
var o = new { foo = 123, bar = true, baz = "this is a test", qux = 123.45, fizzle = DateTime.Now };
Console.WriteLine(StringFormat(format, o));
Performance is pretty ok compared to other solutions.
I doubt this will be possible. The first thing that comes to mind is how are you going to get access to local variable names?
There might be some clever way using LINQ and Lambda expressions to do this however.
Here's one I made a while back. It extends String with a Format method taking a single argument. The nice thing is that it'll use the standard string.Format if you provide a simple argument like an int, but if you use something like anonymous type it'll work too.
Example usage:
"The {Name} family has {Children} children".Format(new { Children = 4, Name = "Smith" })
Would result in "The Smith family has 4 children."
It doesn't do crazy binding stuff like arrays and indexers. But it is super simple and high performance.
public static class AdvancedFormatString
{
/// <summary>
/// An advanced version of string.Format. If you pass a primitive object (string, int, etc), it acts like the regular string.Format. If you pass an anonmymous type, you can name the paramters by property name.
/// </summary>
/// <param name="formatString"></param>
/// <param name="arg"></param>
/// <returns></returns>
/// <example>
/// "The {Name} family has {Children} children".Format(new { Children = 4, Name = "Smith" })
///
/// results in
/// "This Smith family has 4 children
/// </example>
public static string Format(this string formatString, object arg, IFormatProvider format = null)
{
if (arg == null)
return formatString;
var type = arg.GetType();
if (Type.GetTypeCode(type) != TypeCode.Object || type.IsPrimitive)
return string.Format(format, formatString, arg);
var properties = TypeDescriptor.GetProperties(arg);
return formatString.Format((property) =>
{
var value = properties[property].GetValue(arg);
return Convert.ToString(value, format);
});
}
public static string Format(this string formatString, Func<string, string> formatFragmentHandler)
{
if (string.IsNullOrEmpty(formatString))
return formatString;
Fragment[] fragments = GetParsedFragments(formatString);
if (fragments == null || fragments.Length == 0)
return formatString;
return string.Join(string.Empty, fragments.Select(fragment =>
{
if (fragment.Type == FragmentType.Literal)
return fragment.Value;
else
return formatFragmentHandler(fragment.Value);
}).ToArray());
}
private static Fragment[] GetParsedFragments(string formatString)
{
Fragment[] fragments;
if ( parsedStrings.TryGetValue(formatString, out fragments) )
{
return fragments;
}
lock (parsedStringsLock)
{
if ( !parsedStrings.TryGetValue(formatString, out fragments) )
{
fragments = Parse(formatString);
parsedStrings.Add(formatString, fragments);
}
}
return fragments;
}
private static Object parsedStringsLock = new Object();
private static Dictionary<string,Fragment[]> parsedStrings = new Dictionary<string,Fragment[]>(StringComparer.Ordinal);
const char OpeningDelimiter = '{';
const char ClosingDelimiter = '}';
/// <summary>
/// Parses the given format string into a list of fragments.
/// </summary>
/// <param name="format"></param>
/// <returns></returns>
static Fragment[] Parse(string format)
{
int lastCharIndex = format.Length - 1;
int currFragEndIndex;
Fragment currFrag = ParseFragment(format, 0, out currFragEndIndex);
if (currFragEndIndex == lastCharIndex)
{
return new Fragment[] { currFrag };
}
List<Fragment> fragments = new List<Fragment>();
while (true)
{
fragments.Add(currFrag);
if (currFragEndIndex == lastCharIndex)
{
break;
}
currFrag = ParseFragment(format, currFragEndIndex + 1, out currFragEndIndex);
}
return fragments.ToArray();
}
/// <summary>
/// Finds the next delimiter from the starting index.
/// </summary>
static Fragment ParseFragment(string format, int startIndex, out int fragmentEndIndex)
{
bool foundEscapedDelimiter = false;
FragmentType type = FragmentType.Literal;
int numChars = format.Length;
for (int i = startIndex; i < numChars; i++)
{
char currChar = format[i];
bool isOpenBrace = currChar == OpeningDelimiter;
bool isCloseBrace = isOpenBrace ? false : currChar == ClosingDelimiter;
if (!isOpenBrace && !isCloseBrace)
{
continue;
}
else if (i < (numChars - 1) && format[i + 1] == currChar)
{//{{ or }}
i++;
foundEscapedDelimiter = true;
}
else if (isOpenBrace)
{
if (i == startIndex)
{
type = FragmentType.FormatItem;
}
else
{
if (type == FragmentType.FormatItem)
throw new FormatException("Two consequtive unescaped { format item openers were found. Either close the first or escape any literals with another {.");
//curr character is the opening of a new format item. so we close this literal out
string literal = format.Substring(startIndex, i - startIndex);
if (foundEscapedDelimiter)
literal = ReplaceEscapes(literal);
fragmentEndIndex = i - 1;
return new Fragment(FragmentType.Literal, literal);
}
}
else
{//close bracket
if (i == startIndex || type == FragmentType.Literal)
throw new FormatException("A } closing brace existed without an opening { brace.");
string formatItem = format.Substring(startIndex + 1, i - startIndex - 1);
if (foundEscapedDelimiter)
formatItem = ReplaceEscapes(formatItem);//a format item with a { or } in its name is crazy but it could be done
fragmentEndIndex = i;
return new Fragment(FragmentType.FormatItem, formatItem);
}
}
if (type == FragmentType.FormatItem)
throw new FormatException("A format item was opened with { but was never closed.");
fragmentEndIndex = numChars - 1;
string literalValue = format.Substring(startIndex);
if (foundEscapedDelimiter)
literalValue = ReplaceEscapes(literalValue);
return new Fragment(FragmentType.Literal, literalValue);
}
/// <summary>
/// Replaces escaped brackets, turning '{{' and '}}' into '{' and '}', respectively.
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
static string ReplaceEscapes(string value)
{
return value.Replace("{{", "{").Replace("}}", "}");
}
private enum FragmentType
{
Literal,
FormatItem
}
private class Fragment
{
public Fragment(FragmentType type, string value)
{
Type = type;
Value = value;
}
public FragmentType Type
{
get;
private set;
}
/// <summary>
/// The literal value, or the name of the fragment, depending on fragment type.
/// </summary>
public string Value
{
get;
private set;
}
}
}
here is a simple method for any object:
using System.Text.RegularExpressions;
using System.ComponentModel;
public static string StringWithFormat(string format, object args)
{
Regex r = new Regex(#"\{([A-Za-z0-9_]+)\}");
MatchCollection m = r.Matches(format);
var properties = TypeDescriptor.GetProperties(args);
foreach (Match item in m)
{
try
{
string propertyName = item.Groups[1].Value;
format = format.Replace(item.Value, properties[propertyName].GetValue(args).ToString());
}
catch
{
throw new FormatException("The format string is not valid");
}
}
return format;
}
And here how to use it:
DateTime date = DateTime.Now;
string dateString = StringWithFormat("{Month}/{Day}/{Year}", date);
output : 2/27/2012
I implemented this is a simple class that duplicates the functionality of String.Format (except for when using classes). You can either use a dictionary or a type to define fields.
https://github.com/SergueiFedorov/NamedFormatString
C# 6.0 is adding this functionality right into the language spec, so NamedFormatString is for backwards compatibility.
I solved this in a slightly different way to the existing solutions.
It does the core of the named item replacement (not the reflection bit that some have done). It is extremely fast and simple...
This is my solution:
/// <summary>
/// Formats a string with named format items given a template dictionary of the items values to use.
/// </summary>
public class StringTemplateFormatter
{
private readonly IFormatProvider _formatProvider;
/// <summary>
/// Constructs the formatter with the specified <see cref="IFormatProvider"/>.
/// This is defaulted to <see cref="CultureInfo.CurrentCulture">CultureInfo.CurrentCulture</see> if none is provided.
/// </summary>
/// <param name="formatProvider"></param>
public StringTemplateFormatter(IFormatProvider formatProvider = null)
{
_formatProvider = formatProvider ?? CultureInfo.CurrentCulture;
}
/// <summary>
/// Formats a string with named format items given a template dictionary of the items values to use.
/// </summary>
/// <param name="text">The text template</param>
/// <param name="templateValues">The named values to use as replacements in the formatted string.</param>
/// <returns>The resultant text string with the template values replaced.</returns>
public string FormatTemplate(string text, Dictionary<string, object> templateValues)
{
var formattableString = text;
var values = new List<object>();
foreach (KeyValuePair<string, object> value in templateValues)
{
var index = values.Count;
formattableString = ReplaceFormattableItem(formattableString, value.Key, index);
values.Add(value.Value);
}
return String.Format(_formatProvider, formattableString, values.ToArray());
}
/// <summary>
/// Convert named string template item to numbered string template item that can be accepted by <see cref="string.Format(string,object[])">String.Format</see>
/// </summary>
/// <param name="formattableString">The string containing the named format item</param>
/// <param name="itemName">The name of the format item</param>
/// <param name="index">The index to use for the item value</param>
/// <returns>The formattable string with the named item substituted with the numbered format item.</returns>
private static string ReplaceFormattableItem(string formattableString, string itemName, int index)
{
return formattableString
.Replace("{" + itemName + "}", "{" + index + "}")
.Replace("{" + itemName + ",", "{" + index + ",")
.Replace("{" + itemName + ":", "{" + index + ":");
}
}
It is used in the following way:
[Test]
public void FormatTemplate_GivenANamedGuid_FormattedWithB_ShouldFormatCorrectly()
{
// Arrange
var template = "My guid {MyGuid:B} is awesome!";
var templateValues = new Dictionary<string, object> { { "MyGuid", new Guid("{A4D2A7F1-421C-4A1D-9CB2-9C2E70B05E19}") } };
var sut = new StringTemplateFormatter();
// Act
var result = sut.FormatTemplate(template, templateValues);
//Assert
Assert.That(result, Is.EqualTo("My guid {a4d2a7f1-421c-4a1d-9cb2-9c2e70b05e19} is awesome!"));
}
Hope someone finds this useful!
Even though the accepted answer gives some good examples, the .Inject as well as some of the Haack examples do not handle escaping. Many also rely heavily on Regex (slower), or DataBinder.Eval which is not available on .NET Core, and in some other environments.
With that in mind, I've written a simple state machine based parser that streams through characters, writing to a StringBuilder output, character by character. It is implemented as String extension method(s) and can take both a Dictionary<string, object> or object with parameters as input (using reflection).
It handles unlimited levels of {{{escaping}}} and throws FormatException when input contains unbalanced braces and/or other errors.
public static class StringExtension {
/// <summary>
/// Extension method that replaces keys in a string with the values of matching object properties.
/// </summary>
/// <param name="formatString">The format string, containing keys like {foo} and {foo:SomeFormat}.</param>
/// <param name="injectionObject">The object whose properties should be injected in the string</param>
/// <returns>A version of the formatString string with keys replaced by (formatted) key values.</returns>
public static string FormatWith(this string formatString, object injectionObject) {
return formatString.FormatWith(GetPropertiesDictionary(injectionObject));
}
/// <summary>
/// Extension method that replaces keys in a string with the values of matching dictionary entries.
/// </summary>
/// <param name="formatString">The format string, containing keys like {foo} and {foo:SomeFormat}.</param>
/// <param name="dictionary">An <see cref="IDictionary"/> with keys and values to inject into the string</param>
/// <returns>A version of the formatString string with dictionary keys replaced by (formatted) key values.</returns>
public static string FormatWith(this string formatString, IDictionary<string, object> dictionary) {
char openBraceChar = '{';
char closeBraceChar = '}';
return FormatWith(formatString, dictionary, openBraceChar, closeBraceChar);
}
/// <summary>
/// Extension method that replaces keys in a string with the values of matching dictionary entries.
/// </summary>
/// <param name="formatString">The format string, containing keys like {foo} and {foo:SomeFormat}.</param>
/// <param name="dictionary">An <see cref="IDictionary"/> with keys and values to inject into the string</param>
/// <returns>A version of the formatString string with dictionary keys replaced by (formatted) key values.</returns>
public static string FormatWith(this string formatString, IDictionary<string, object> dictionary, char openBraceChar, char closeBraceChar) {
string result = formatString;
if (dictionary == null || formatString == null)
return result;
// start the state machine!
// ballpark output string as two times the length of the input string for performance (avoids reallocating the buffer as often).
StringBuilder outputString = new StringBuilder(formatString.Length * 2);
StringBuilder currentKey = new StringBuilder();
bool insideBraces = false;
int index = 0;
while (index < formatString.Length) {
if (!insideBraces) {
// currently not inside a pair of braces in the format string
if (formatString[index] == openBraceChar) {
// check if the brace is escaped
if (index < formatString.Length - 1 && formatString[index + 1] == openBraceChar) {
// add a brace to the output string
outputString.Append(openBraceChar);
// skip over braces
index += 2;
continue;
}
else {
// not an escaped brace, set state to inside brace
insideBraces = true;
index++;
continue;
}
}
else if (formatString[index] == closeBraceChar) {
// handle case where closing brace is encountered outside braces
if (index < formatString.Length - 1 && formatString[index + 1] == closeBraceChar) {
// this is an escaped closing brace, this is okay
// add a closing brace to the output string
outputString.Append(closeBraceChar);
// skip over braces
index += 2;
continue;
}
else {
// this is an unescaped closing brace outside of braces.
// throw a format exception
throw new FormatException($"Unmatched closing brace at position {index}");
}
}
else {
// the character has no special meaning, add it to the output string
outputString.Append(formatString[index]);
// move onto next character
index++;
continue;
}
}
else {
// currently inside a pair of braces in the format string
// found an opening brace
if (formatString[index] == openBraceChar) {
// check if the brace is escaped
if (index < formatString.Length - 1 && formatString[index + 1] == openBraceChar) {
// there are escaped braces within the key
// this is illegal, throw a format exception
throw new FormatException($"Illegal escaped opening braces within a parameter - index: {index}");
}
else {
// not an escaped brace, we have an unexpected opening brace within a pair of braces
throw new FormatException($"Unexpected opening brace inside a parameter - index: {index}");
}
}
else if (formatString[index] == closeBraceChar) {
// handle case where closing brace is encountered inside braces
// don't attempt to check for escaped braces here - always assume the first brace closes the braces
// since we cannot have escaped braces within parameters.
// set the state to be outside of any braces
insideBraces = false;
// jump over brace
index++;
// at this stage, a key is stored in current key that represents the text between the two braces
// do a lookup on this key
string key = currentKey.ToString();
// clear the stringbuilder for the key
currentKey.Clear();
object outObject;
if (!dictionary.TryGetValue(key, out outObject)) {
// the key was not found as a possible replacement, throw exception
throw new FormatException($"The parameter \"{key}\" was not present in the lookup dictionary");
}
// we now have the replacement value, add the value to the output string
outputString.Append(outObject);
// jump to next state
continue;
} // if }
else {
// character has no special meaning, add it to the current key
currentKey.Append(formatString[index]);
// move onto next character
index++;
continue;
} // else
} // if inside brace
} // while
// after the loop, if all braces were balanced, we should be outside all braces
// if we're not, the input string was misformatted.
if (insideBraces) {
throw new FormatException("The format string ended before the parameter was closed.");
}
return outputString.ToString();
}
/// <summary>
/// Creates a Dictionary from an objects properties, with the Key being the property's
/// name and the Value being the properties value (of type object)
/// </summary>
/// <param name="properties">An object who's properties will be used</param>
/// <returns>A <see cref="Dictionary"/> of property values </returns>
private static Dictionary<string, object> GetPropertiesDictionary(object properties) {
Dictionary<string, object> values = null;
if (properties != null) {
values = new Dictionary<string, object>();
PropertyDescriptorCollection props = TypeDescriptor.GetProperties(properties);
foreach (PropertyDescriptor prop in props) {
values.Add(prop.Name, prop.GetValue(properties));
}
}
return values;
}
}
Ultimately, all the logic boils down into 10 main states - For when the state machine is outside a bracket and likewise inside a bracket, the next character is either an open brace, an escaped open brace, a closed brace, an escaped closed brace, or an ordinary character. Each of these conditions is handled individually as the loop progresses, adding characters to either an output StringBuffer or a key StringBuffer. When a parameter is closed, the value of the key StringBuffer is used to look up the parameter's value in the dictionary, which then gets pushed into the output StringBuffer. At the end, the value of the output StringBuffer is returned.
string language = "Python";
int numquotes = 2;
string output = language + " has "+ numquotes + " language types.";
Edit:
What I should have said was, "No, I don't believe what you want to do is supported by C#. This is as close as you are going to get."
I have a string that can look like this: 12345, this 123456 or this: 1234567.
I'd like to make each string look like this: 123-45, this: 1234-56 or this: 12345-67.
How can I do this in C#?
string myString = "1234567";
if(myString.Length > 1)
string dashed = myString.Insert(myString.Length - 2, "-");
EDIT: Added check based on comment, but depends on how such strings should be handled. (e.g. dashed even if length = 2?)
Take a look at String.Format(), My guess is you want something like String.Format("{0:##-##}",< value >);
http://msdn.microsoft.com/en-us/library/0c899ak8.aspx
Examples shown with powershell, which uses the same corelibs
PS C:\Users\Phyx> [string]::Format("{0:##-##}",1234)
12-34
PS C:\Users\Phyx> [string]::Format("{0:##-##}",123445)
1234-45
PS C:\Users\Phyx> [string]::Format("{0:##-##}",12)
-12
PS C:\Users\Phyx> [string]::Format("{0:0#-##}",12)
00-12
PS C:\Users\Phyx> [string]::Format("{0:##-##}",122)
1-22
I'm assuming you want to add a dash two characters before the end of the string.
string number = "12345";
if(number.Length > 2)
string result = number.Insert(number.Length-2, "-");
else
//error checking
string s = "teststring";
string newString = s.Insert(s.Length-2,"-");
This is assuming you want the '-' to appear two from the end :-)
This could be handy (untested)
/// <summary>
/// Takes a string and and inserts a spacer character at
/// a specifed distance from the end
/// </summary>
/// <param name="input">string to modify</param>
/// <param name="spacer">string to insert</param>
/// <param name="positionFromEnd">insertion point</param>
/// <returns></returns>
protected string AddSpacer(string input, string spacer, int positionFromEnd)
{
string outputString = string.Empty;
if (input.Length >= positionFromEnd)
{
outputString = input.Insert(input.Length - positionFromEnd, spacer);
}
else
{
throw new Exception("The position you tried to insert the spacer into doesn't exist");
}
return outputString;
}
I'm writing automatic e-mailer. It has to scan database every X minutes and email people with reminders etc.
I have all underlying code ready. All I need now is to format emails.
Is there any predefined templating system in C# so I can create a folder with different templates and eg. tags such as {NAME} so I just find those and replace it.
I can do it manually with opening a *.txt document and replacing those specific tags etc, however is there anything smarter? I wouldn't want to reinvent the wheel.
I'd look at using StringTemplate: http://www.stringtemplate.org/
You can do it with MVC 3's Razor templates, even in non-web applications.
An Internet search for Razor templates non-web will turn up many examples.
It's not too difficult to write from scratch. I wrote this quick utility to do exactly what you described. It looks for tokens in the pattern {token} and replaces them with the value that it retrieves from the NameValueCollection. Tokens in the string correspond to keys in the collection which get replaced out for the value of the key in the collection.
It also has the added bonus of being simple enough to customize exactly as you need it.
public static string ReplaceTokens(string value, NameValueCollection tokens)
{
if (tokens == null || tokens.Count == 0 || string.IsNullOrEmpty(value)) return value;
string token = null;
foreach (string key in tokens.Keys)
{
token = "{" + key + "}";
value = value.Replace(token, tokens[key]);
}
return value;
}
USAGE:
public static bool SendEcard(string fromName, string fromEmail, string toName, string toEmail, string message, string imageUrl)
{
var body = GetEmailBody();
var tokens = new NameValueCollection();
tokens["sitedomain"] = "http://example.com";
tokens["fromname"] = fromName;
tokens["fromemail"] = fromEmail;
tokens["toname"] = toName;
tokens["toemail"] = toEmail;
tokens["message"] = message;
tokens["image"] = imageUrl;
var msg = CreateMailMessage();
msg.Body = StringUtility.ReplaceTokens(body, tokens);
//...send email
}
You can use the nVelocity
string templateDir = HttpContext.Current.Server.MapPath("Templates");
string templateName = "SimpleTemplate.vm";
INVelocityEngine fileEngine =
NVelocityEngineFactory.CreateNVelocityFileEngine(templateDir, true);
IDictionary context = new Hashtable();
context.Add(parameterName , value);
var output = fileEngine.Process(context, templateName);
If you are using ASP.NET 4 you can download RazorMail from the Nuget Gallery. It allows creation of emails using the Razor View Engine outwith the context of an MVC http request.
More details can be found via the following links...
http://www.nuget.org/List/Packages/RazorMail
https://github.com/wduffy/RazorMail/
I use this alot, plug in a Regex and a method that selects the replacement value based on the match.
/// </summary>
/// <param name="input">The text to perform the replacement upon</param>
/// <param name="pattern">The regex used to perform the match</param>
/// <param name="fnReplace">A delegate that selects the appropriate replacement text</param>
/// <returns>The newly formed text after all replacements are made</returns>
public static string Transform(string input, Regex pattern, Converter<Match, string> fnReplace)
{
int currIx = 0;
StringBuilder sb = new StringBuilder();
foreach (Match match in pattern.Matches(input))
{
sb.Append(input, currIx, match.Index - currIx);
string replace = fnReplace(match);
sb.Append(replace);
currIx = match.Index + match.Length;
}
sb.Append(input, currIx, input.Length - currIx);
return sb.ToString();
}
Example Usage
Dictionary<string, string> values = new Dictionary<string, string>();
values.Add("name", "value");
TemplateValues tv = new TemplateValues(values);
Assert.AreEqual("valUE", tv.ApplyValues("$(name:ue=UE)"));
/// <summary>
/// Matches a makefile macro name in text, i.e. "$(field:name=value)" where field is any alpha-numeric + ('_', '-', or '.') text identifier
/// returned from group "field". the "replace" group contains all after the identifier and before the last ')'. "name" and "value" groups
/// match the name/value replacement pairs.
/// </summary>
class TemplateValues
{
static readonly Regex MakefileMacro = new Regex(#"\$\((?<field>[\w-_\.]*)(?<replace>(?:\:(?<name>[^:=\)]+)=(?<value>[^:\)]*))+)?\)");
IDictionary<string,string> _variables;
public TemplateValues(IDictionary<string,string> values)
{ _variables = values; }
public string ApplyValues(string template)
{
return Transform(input, MakefileMacro, ReplaceVariable);
}
private string ReplaceVariable(Match m)
{
string value;
string fld = m.Groups["field"].Value;
if (!_variables.TryGetValue(fld, out value))
{
value = String.Empty;
}
if (value != null && m.Groups["replace"].Success)
{
for (int i = 0; i < m.Groups["replace"].Captures.Count; i++)
{
string replace = m.Groups["name"].Captures[i].Value;
string with = m.Groups["value"].Captures[i].Value;
value = value.Replace(replace, with);
}
}
return value;
}
}
(Even though you've ticked an answer, for future reference) - I got some amazing responses on my question of a similar nature: Which approach to templating in C sharp should I take?