This isn't a serious problem, I was just curious.
I am formatting a string, the data in the output string reuses argument data several times, but changes the case (for example).
string data = "TEST";
string s = string.Format("{0} - {1}", data, data.ToLower());
// REQUIRED OUTPUT
// TEST - test
But can I achieve this somehow...
// ****PSEUDO-code****
//string s = string.Format("{0} - {0}.ToLower()", data);
There are many specifiers that allow you to format the data that replaces the formatting token (this article is a good place to learn about those).
Unfortunately there is no specifier that lets you do a ToLower on the string - you will have to do that yourself before you pass it to String.Format.
What you want to do is not possible.
When you pass in a string argument to string.Format it is left unchanged (barring alignment/width). There is no way to specify composite formatting that will manipulate a passed in string to change its case.
Related
Numerical formatting of int, double, decimal can be simply achieved via using Standard Numerical Formatter for example assuming Culture is "en-GB":
int value = 1000;
Console.WriteLine(value.ToString("C0")); // Would output £1,000
However I am wondering if there is a simple way to format a string to something of the same effect as above. For example:
string amount = "£2000"; // Would want to format to "£2,000"
Is there a way to format this string so that the thousands separator is added in the correct position?
Given it's a string I don't think numerical formatting would work without converting the string to a numerical data type beforehand:
var result = Int32.Parse("£2000", NumberStyles.AllowCurrencySymbol, new CultureInfo("en-GB"));
Console.WriteLine(result.ToString("C0", new CultureInfo("en-GB"))); // Outputs £2,000
However its a bit verbose to convert string to int then back to string. Is there is a simpler way to do this given that the starting string has the currency symbol?
Given it's a string I don't think numerical formatting would work without converting the string to a numerical data type beforehand
Indeed.
Is there is a simpler way to do this given that the starting string has the currency symbol?
No. And I seriously doubt that such a feature would ever be added and/or welcomed by the developer community. A formal specification for such a feature would be a complexity nightmare.
Of course, in your particular case, if you are sure that your string always consists of "currency symbol + sequence of digits without comma or period", you could develop a string-based solution optimized for your use case (for example, a fancy regular expression). However, I think that your current solution is both readable and maintainable and you would do your future self a favor by keeping it that way. If you need it multiple times, extract it into a method.
I have the following scenario.I am using App.config in Winforms and I have a value that is set to int (In settings). I want to use this value as a label text.
Am I correct that labels can only display string values?
This is what I have done here but not getting expected result (value to the label):
int ExclRate = Properties.Settings.Default.PriorExclTimer;
string ExclTime = ExclRate.ToString();
ExclTime = label60.Text;
PriorExclTimer is the type of the value in app.config.
I can make this work if I set the value in app.config to string, but that means I would have to convert from string to int in a much more sensitive part of the program, and I would rather not have to do that if possible. This is that line that works:
label60.Text = Properties.Settings.Default.PriorExclTimer;
I'm very new to C#, so I am really feeling my way around. Thanks...
In C# you cannot directly assign int to string. It has to always undergo conversion (either parse string to integer, or get a string out of integer).
As you say it's better to convert integer to a string for display purposes. Labels cannot directly show integer, so you will always need to convert it, or write some wrapper class if it's not enough.
Be aware that ToString() is culture specific, i.e. it will use the culture from the current thread. It might or might not be what you want. If you want InvariantCulture you can use ToString(CultureInfo.InvariantCulture).
P.S. As mentioned in the comments you can do various tricks like ExclRate + "", or in C#6 ${ExclRate}, but they are all basically converting an integer to string. I guess they all call ToString() inside.
int ExclRate = Properties.Settings.Default.PriorExclTimer;
label60.Text = ExclRate.ToString();
Code above will give you exception if PriorExclTimer is null or empty. So better you use int.TryParse to assign it to int. Not in this case, but ToString does not handle the null case, it gives exception. So you should try Convert.ToString instead.
While doing string manipulations you have to take care of culture and case (string case sensitive or insensitive)
This works for me:
int ExclRate = Properties.Settings.Default.PriorExclTimer;
label60.Text = ExclRate.ToString();
Many thanks for the insights on this topic. I will be manipulating data to and from a string a good bit for the project I am working on...
I'm writing a little text-based adventure in the console as one of my first projects in C#.
At a certain point, I want to do the following:
Console.WriteLine(intro);
var name = Console.ReadLine();
Console.Clear();
Console.WriteLine(replyOne, name, replyTwo);
However, on that last line, only the first variable (replyOne) is displayed. How can I display all the values?
Depends on what's on replyOne, but you are using a Console.WriteLine overload that takes a format string as the first argument and a number of objects for substitution of that format string (this one). That's what's called Composite Formatting in .NET
If what you want to do is concatenate the strings, you can do it in several ways:
Pass only one string to Console.WriteLine:
Console.WriteLine(replyOne + name + replyTwo);
Use a format string... this would use the same overload you are using now, but passing a formatting string for substitution on the first argument:
Console.WriteLine("{0}{1}{2}", replyOne, name, replyTwo);
Use an interpolated string (C# 6 and up only)
Console.WriteLine($"{replyOne}{name}{replyTwo}");
In the multi-argument overloads of the Console.WriteLine the first parameter is supposed to be a format string, and everything else as a substitution values.
See Console.WriteLine Method (String, Object) for details.
If you want Console.WriteLine to output a formatted string the first argument has to be the string that contains the placeholders that define the formatting. So assuming you just want to output the three strings consecutively, you'll need something like this:
Console.WriteLine("{0} {1} {2}", replyOne, name, replyTwo);
which will output the three strings separated by spaces.
You can replace the spaces by commas, newlines (\n) or tabs (\t) to get the formatting you need.
Try this instead:
Console.WriteLine(replyOne + name + replyTwo);
Or something similar.
As you're calling the method right now, it's treating the replyOne value as the format for the output, not an individual output item. And of course, your format doesn't have a {0} or {1} for the format arguments in the call, name and replyTwo, so they are omitted.
You can just concatenate the output text yourself, as above, as use that as the entire format (without any format arguments at all).
There are, of course, lots of other options for formatting the output. The above fits what you've posted so far.
Console.WriteLine("{0},{1},{2}",replyOne,name,replyTwo);
When I learned about the String.Format function, I did the mistake to think that it's acceptable to name the placeholders after the colon, so I wrote code like this:
String.Format("A message: '{0:message}'", "My message");
//output: "A message: 'My message'"
I just realized that the string behind the colon is used to define the format of the placeholder and may not be used to add a comment as I did.
But apparently, the string behind the colon is used for the placeholder if:
I want to fill the placeholder with an integer and
I use an unrecognized formating-string behind the colon
But this doesn't explain to me, why the string behind the colon is used for the placeholder if I provide an integer.
Some examples:
//Works for strings
String.Format("My number is {0:number}!", "10")
//output: "My number is 10!"
//Works without formating-string
String.Format("My number is {0}!", 10)
//output: "My number is 10!"
//Works with recognized formating string
String.Format("My number is {0:d}!", 10)
//output: "My number is 10!"
//Does not work with unrecognized formating string
String.Format("My number is {0:number}!", 10)
//output: "My number is number!"
Why is there a difference between the handling of strings and integers? And why is the fallback to output the formating string instead of the given value?
Just review the MSDN page about composite formatting for clarity.
A basic synopsis, the format item syntax is:
{ index[,alignment][:formatString]}
So what appears after the : colon is the formatString. Look at the "Format String Component" section of the MSDN page for what kind of format strings are predefined. You will not see System.String mentioned in that list. Which is no great surprise, a string is already "formatted" and will only ever appear in the output as-is.
Composite formatting is pretty lenient to mistakes, it won't throw an exception when you specify an illegal format string. That the one you used isn't legal is already pretty evident from the output you get. And most of all, the scheme is extensible. You can actually make a :message format string legal, a class can implement the ICustomFormatter interface to implement its own custom formatting. Which of course isn't going to happen on System.String, you cannot modify that class.
So this works as expected. If you don't get the output you expected then this is pretty easy to debug, you've just go two mistakes to consider. The debugger eliminates one (wrong argument), your eyes eliminates the other.
String.Format article on MSDN has following description:
A format item has this syntax: { index[,alignment][ :formatString] }
...
formatString Optional.
A string that specifies the format of the
corresponding argument's result string. If you omit formatString, the
corresponding argument's parameterless ToString method is called to
produce its string representation. If you specify formatString, the
argument referenced by the format item must implement the IFormattable
interface.
If we directly format the value using the IFormattable we will have the same result:
String garbageFormatted = (10 as IFormattable).ToString("garbage in place of int",
CultureInfo.CurrentCulture.NumberFormat);
Console.WriteLine(garbageFormatted); // Writes the "garbage in place of int"
So it seems that it is something close to the "garbage in, garbage out" problem in the implementation of the IFormattable interface on Int32 type(and possibly on other types as well). The String class does not implement IFormattable, so any format specifier is left unused and .ToString(IFormatProvider) is called instead.
Also:
Ildasm shows that Int32.ToString(String, INumberFormat) internally calls
string System.Number::FormatInt32(int32,
string,
class System.Globalization.NumberFormatInfo)
But it is the internalcall method (extern implemented somewhere in native code), so Ildasm is of no use if we want to determine the source of the problem.
EDIT - CULPRIT:
After reading the How to see code of method which marked as MethodImplOptions.InternalCall? I've used the source code from Shared Source Common Language Infrastructure 2.0 Release (it is .NET 2.0 but nonetheless) in attempt to find a culprit.
Code for the Number.FormatInt32 is located in the ...\sscli20\clr\src\vm\comnumber.cpp file.
The culprit could be deduced from the default section of the format switch statement of the FCIMPL3(Object*, COMNumber::FormatInt32, INT32 value, StringObject* formatUNSAFE, NumberFormatInfo* numfmtUNSAFE):
default:
NUMBER number;
Int32ToNumber(value, &number);
if (fmt != 0) {
gc.refRetString = NumberToString(&number, fmt, digits, gc.refNumFmt);
break;
}
gc.refRetString = NumberToStringFormat(&number, gc.refFormat, gc.refNumFmt);
break;
The fmt var is 0, so the NumberToStringFormat(&number, gc.refFormat, gc.refNumFmt); is being called.
It leads us to nothing else than to the second switch statement default section in the NumberToStringFormat method, that is located in the loop that enumerates every format string character. It is very simple:
default:
*dst++ = ch;
It just plain copies every character from the format string into the output array, that's how the format string ends repeated in the output.
From one point of view it allows to really use garbage format strings that will output nothing useful, but from other point of view it will allow you to use something like:
String garbageFormatted = (1234 as IFormattable).ToString("0 thousands and ### in thousand",
CultureInfo.CurrentCulture.NumberFormat);
Console.WriteLine(garbageFormatted);
// Writes the "1 thousands and 234 in thousand"
that can be handy in some situations.
Interesting behavior indeed BUT NOT unaccounted for.
Your last example works when
if String.Format("My number is {0:n}!", 10)
but revert to the observed beahvior when
if String.Format("My number is {0:nu}!", 10)`.
This prompts to search about the Standard Numeric Format Specifier article on MSDN where you can read
Standard numeric format strings are used to format common numeric
types. A standard numeric format string takes the form Axx, where:
A is a single alphabetic character called the format specifier. Any
numeric format string that contains more than one alphabetic
character, including white space, is interpreted as a custom numeric
format string. For more information, see Custom Numeric Format
Strings.
The same article explains: if you have a SINGLE letter that is not recognized you get an exception.
Indeed
if String.Format("My number is {0:K}!", 10)`.
throws the FormatException as explained.
Now looking in the Custom Numeric Format Strings chapter you will find a table of eligible letters and their possible mixings, but at the end of the table you could read
Other
All other characters
The character is copied to the result string unchanged.
So I think that you have created a format string that cannot in any way print that number because there is no valid format specifier where the number 10 should be 'formatted'.
No it's not acceptable to place anything you like after the colon. Putting anything other than a recognized format specifier is likely to result in either an exception or unpredictable behaviour as you've demonstrated. I don't think you can expect string.Format to behave consistently when you're passing it arguments which are completely inconsistent with the documented formatting types
What would be the best way to accomplish something like this?
Suppose I have the following pair of Resource strings.
BadRequestParameter: Potential bad request aborted before execution.
RequiredParameterConstraint: {0} parameter requires a value. {1}
And suppose I want to set {1} on the second one, to the value of BadRequestParameter. I could easily do that using string.Format. But now suppose I have lots of Resource strings like the second one, all of which include some other Resource string in them.
What would be the best way to code this? Is using string.Format repeateadly in each case really all that I can do?
Update
I'll try to explain myself better. These are the resource strings I actually have:
BadRequestParameter Potential bad request aborted before execution.
EmptyVector Vectorized requests require at least one element. {0}
OverflownVector Vectorized requests can take at most one hundred elements. {0}
RequiredParamConstraint {0} parameter requires a value. {1}
SortMinMaxConstraint {0} parameter value '{1}' does not allow Min or Max parameters in this query. {2}
SortRangeTypeConstraint Expected {0} parameter Type '{1}'. Actual: '{2}'. {3}
SortValueConstraint {0} parameter does not allow '{1}' as a value in this query. {2}
I'd like to avoid writing the string in BadRequestParameter at the end of each of those lines. Therefore, I added a format at the end of those strings. The issue now is that I'd like to somehow auto-reference {x} to BadRequestParameter, in order to avoid having to make calls like
string.Format(Error.EmptyVector, Error.BadRequestParameter);
I have lots of Resource strings like the second one, all of which include some other Resource string in them.
Instead of storing pre-made format strings ready for use, you could store raw material for building real format strings, and add code to expand them pro grammatically before use. For example, you could store strings like this:
BadRequestParameter: Potential bad request aborted before execution.
SupportNumber: (123)456-7890
CallTechSupport: You need to call technical support at {SupportNumber}.
RequiredParameterConstraint: {{0}} parameter requires a value. {BadRequestParameter} {CallTechSupport}
Of course passing these strings to string.Format as-is is not going to work. You need to parse these strings, for example with RegExps, and find all instances where you have a word between curly braces, instead of a number. You could then replace each word with its sequence number, and produce an array of parameters based on the names that you find between curly braces. In this case, you will get these two values (pseudocode):
formatString = "{{0}} parameter requires a value. {0} {1}";
// You replaced {BadRequestParameter} with {0} and {CallTechSupport} with {1}
parameters = {
"Potential bad request aborted before execution."
, "You need to call technical support at (123)456-7890."
};
Note: Of course, producing this array of parameters required recursion.
At this point, you can invoke string.Format to produce your final string:
var res = string.Format(formatString, parameters);
This returns the string that has resource strings pre-replaced for your callers:
"{0} parameter requires a value. Potential bad request aborted before execution. You need to call technical support at (123)456-7890."
The callers can now use this string for formatting, without bothering with other resource values.
Yes :-) unless you want to make a helper method that is shorter, but that would really just be for convenience sake
public static string f(string format, params object[] p)
{
return string.Format(format, p);
}
IF you treat the argument indicators {#} as wild cards then why would it make sense for you to pre-fill them inside of your resource.
I see absolutely nothing wrong with
String.Format(RequiredParamterConstraint, "something", BadRequestParameter);