I have a lot of if, else if statements and I know there has to be a better way to do this but even after searching stackoverflow I'm unsure of how to do so in my particular case.
I am parsing text files (bills) and assigning the name of the service provider to a variable (txtvar.Provider) based on if certain strings appear on the bill.
This is a small sample of what I'm doing (don't laugh, I know it's messy). All in all, There are approximately 300 if, else if's.
if (txtvar.BillText.IndexOf("SWGAS.COM") > -1)
{
txtvar.Provider = "Southwest Gas";
}
else if (txtvar.BillText.IndexOf("georgiapower.com") > -1)
{
txtvar.Provider = "Georgia Power";
}
else if (txtvar.BillText.IndexOf("City of Austin") > -1)
{
txtvar.Provider = "City of Austin";
}
// And so forth for many different strings
I would like to use something like a switch statement to be more efficient and readable but I'm unsure of how I would compare the BillText. I'm looking for something like this but can't figure out how to make it work.
switch (txtvar.BillText)
{
case txtvar.BillText.IndexOf("Southwest Gas") > -1:
txtvar.Provider = "Southwest Gas";
break;
case txtvar.BillText.IndexOf("TexasGas.com") > -1:
txtvar.Provider = "Texas Gas";
break;
case txtvar.BillText.IndexOf("Southern") > -1:
txtvar.Provider = "Southern Power & Gas";
break;
}
I'm definitely open to ideas.
I would need the ability to determine the order in which the values were evaluated.
As you can imagine, when parsing for hundreds of slightly different layouts I occasionally run into the issue of not having a distinctly unique indicator as to what service provider the bill belongs to.
Why not use everything C# has to offer? The following use of anonymous types, collection initializers, implicitly typed variables, and lambda-syntax LINQ is compact, intuitive, and maintains your modified requirement that patterns be evaluated in order:
var providerMap = new[] {
new { Pattern = "SWGAS.COM" , Name = "Southwest Gas" },
new { Pattern = "georgiapower.com", Name = "Georgia Power" },
// More specific first
new { Pattern = "City of Austin" , Name = "City of Austin" },
// Then more general
new { Pattern = "Austin" , Name = "Austin Electric Company" }
// And for everything else:
new { Pattern = String.Empty , Name = "Unknown" }
};
txtVar.Provider = providerMap.First(p => txtVar.BillText.IndexOf(p.Pattern) > -1).Name;
More likely, the pairs of patterns would come from a configurable source, such as:
var providerMap =
System.IO.File.ReadLines(#"C:\some\folder\providers.psv")
.Select(line => line.Split('|'))
.Select(parts => new { Pattern = parts[0], Name = parts[1] }).ToList();
Finally, as #millimoose points out, anonymous types are less useful when passed between methods. In that case we can define a trival Provider class and use object initializers for nearly identical syntax:
class Provider {
public string Pattern { get; set; }
public string Name { get; set; }
}
var providerMap =
System.IO.File.ReadLines(#"C:\some\folder\providers.psv")
.Select(line => line.Split('|'))
.Select(parts => new Provider() { Pattern = parts[0], Name = parts[1] }).ToList();
Since you seem to need to search for the key before returning the value a Dictionary is the right way to go, but you will need to loop over it.
// dictionary to hold mappings
Dictionary<string, string> mapping = new Dictionary<string, string>();
// add your mappings here
// loop over the keys
foreach (KeyValuePair<string, string> item in mapping)
{
// return value if key found
if(txtvar.BillText.IndexOf(item.Key) > -1) {
return item.Value;
}
}
EDIT: If you wish to have control over the order in which elemnts are evaluated, use an OrderedDictionary and add the elements in the order in which you want them evaluated.
One more using LINQ and Dictionary
var mapping = new Dictionary<string, string>()
{
{ "SWGAS.COM", "Southwest Gas" },
{ "georgiapower.com", "Georgia Power" }
.
.
};
return mapping.Where(pair => txtvar.BillText.IndexOf(pair.Key) > -1)
.Select(pair => pair.Value)
.FirstOrDefault();
If we prefer empty string instead of null when no key matches we can use the ?? operator:
return mapping.Where(pair => txtvar.BillText.IndexOf(pair.Key) > -1)
.Select(pair => pair.Value)
.FirstOrDefault() ?? "";
If we should consider the dictionary contains similar strings we add an order by, alphabetically, shortest key will be first, this will pick 'SCE' before 'SCEC'
return mapping.Where(pair => txtvar.BillText.IndexOf(pair.Key) > -1)
.OrderBy(pair => pair.Key)
.Select(pair => pair.Value)
.FirstOrDefault() ?? "";
To avoid the blatant Schlemiel the Painter's approach that looping over all the keys would involve: let's use regular expressions!
// a dictionary that holds which bill text keyword maps to which provider
static Dictionary<string, string> BillTextToProvider = new Dictionary<string, string> {
{"SWGAS.COM", "Southwest Gas"},
{"georgiapower.com", "Georgia Power"}
// ...
};
// a regex that will match any of the keys of this dictionary
// i.e. any of the bill text keywords
static Regex BillTextRegex = new Regex(
string.Join("|", // to alternate between the keywords
from key in BillTextToProvider.Keys // grab the keywords
select Regex.Escape(key))); // escape any special characters in them
/// If any of the bill text keywords is found, return the corresponding provider.
/// Otherwise, return null.
string GetProvider(string billText)
{
var match = BillTextRegex.Match(billText);
if (match.Success)
// the Value of the match will be the found substring
return BillTextToProvider[match.Value];
else return null;
}
// Your original code now reduces to:
var provider = GetProvider(txtvar.BillText);
// the if is be unnecessary if txtvar.Provider should be null in case it can't be
// determined
if (provider != null)
txtvar.Provider = provider;
Making this case-insensitive is a trivial exercise for the reader.
All that said, this does not even pretend to impose an order on which keywords to look for first - it will find the match that's located earliest in the string. (And then the one that occurs first in the RE.) You do however mention that you're searching through largeish texts; if .NET's RE implementation is at all good this should perform considerably better than 200 naive string searches. (By only making one pass through the string, and maybe a little by merging common prefixes in the compiled RE.)
If ordering is important to you, you might want to consider looking for an implementation of a better string search algorithm than .NET uses. (Like a variant of Boyer-Moore.)
What you want is a Dictionary:
Dictionary<string, string> mapping = new Dictionary<string, string>();
mapping["SWGAS.COM"] = "Southwest Gas";
mapping["foo"] = "bar";
... as many as you need, maybe read from a file ...
Then just:
return mapping[inputString];
Done.
One way of doing it (other answers show very valid options):
void Main()
{
string input = "georgiapower.com";
string output = null;
// an array of string arrays...an array of Tuples would also work,
// or a List<T> with any two-member type, etc.
var search = new []{
new []{ "SWGAS.COM", "Southwest Gas"},
new []{ "georgiapower.com", "Georgia Power"},
new []{ "City of Austin", "City of Austin"}
};
for( int i = 0; i < search.Length; i++ ){
// more complex search logic could go here (e.g. a regex)
if( input.IndexOf( search[i][0] ) > -1 ){
output = search[i][1];
break;
}
}
// (optional) check that a valid result was found.
if( output == null ){
throw new InvalidOperationException( "A match was not found." );
}
// Assign the result, output it, etc.
Console.WriteLine( output );
}
The main thing to take out of this exercise is that creating a giant switch or if/else structure is not the best way to do it.
There are several approaches to do this, but for the reason of simplicity, conditional operator may be a choice:
Func<String, bool> contains=x => {
return txtvar.BillText.IndexOf(x)>-1;
};
txtvar.Provider=
contains("SWGAS.COM")?"Southwest Gas":
contains("georgiapower.com")?"Georgia Power":
contains("City of Austin")?"City of Austin":
// more statements go here
// if none of these matched, txtvar.Provider is assigned to itself
txtvar.Provider;
Note the result is according to the more preceded condition which is met, so if txtvar.BillText="City of Austin georgiapower.com"; then the result would be "Georgia Power".
you can use dictionary.
Dictionary<string, string> textValue = new Dictionary<string, string>();
foreach (KeyValuePair<string, string> textKey in textValue)
{
if(txtvar.BillText.IndexOf(textKey.Key) > -1)
return textKey.Value;
}
Related
I have a method that takes a List<Dictionary<string,object>> as a parameter. The plan is to use that parameter, but only update the values held in a particular class. Here is the (partially written) method
public async Task<Errors> UpdatePageForProject(Guid projectId, List<Dictionary<string, object>> data)
{
if (!IsValidUserIdForProject(projectId))
return new Errors { ErrorMessage = "Project does not exist", Success = false };
if (data.Count == 0)
return new Errors { ErrorMessage = "No data passed to change", Success = false };
var page = await _context.FlowPages.FirstOrDefaultAsync(t => t.ProjectId == projectId);
foreach (var d in data)
{
}
return new Errors { Success = true };
}
My original plan is to take each dictionary, check if the key and the property in page match and then alter the value (so I can pass in 1 dictionary or 8 dictionaries in the list and then alter page to save back to my entity database).
I'd rather not use reflection due to the speed hit (though C#9 is really fast, I'd still rather not use it), but I'm not sure how else this can be done. I did consider using AutoMapper to do this, but for now would rather not (it's a PoC, so it is possibly overkill)
If you want to do this without Reflection (which I agree is a good idea, not just for performance reasons) then you could use a "map" or lookup table with actions for each property.
var map = new Dictionary<string,Action<Page,object>>()
{
{ "Title", (p,o) => p.Title = (string)o },
{ "Header", (p,o) => p.Field1 = (string)o },
{ "DOB", (p,o) => p.DateOfBirth = (DateTime)o }
};
You can then iterate over your list of dictionaries and use the map to execute actions that update the page.
foreach (var dictionary in data)
{
foreach (entry in dictionary)
{
var action = map[entry.Key];
action(page, entry.Value);
}
}
If We have a list of strings like the following code:
List<string> XAll = new List<string>();
XAll.Add("#10#20");
XAll.Add("#20#30#40");
string S = "#30#20";//<- this is same as #20#30 also same as "#20#30#40" means S is exist in that list
//check un-ordered string S= #30#20
// if it is contained at any order like #30#20 or even #20#30 ..... then return true :it is exist
if (XAll.Contains(S))
{
Console.WriteLine("Your String is exist");
}
I would prefer to use Linq to check that S in this regard is exist, no matter how the order is in the list, but it contains both (#30) and (#20) [at least] together in that list XAll.
I am using
var c = item2.Intersect(item1);
if (c.Count() == item1.Length)
{
return true;
}
You should represent your data in a more meaningful way. Don't rely on strings.
For example I would suggest creating a type to represent a set of these numbers and write some code to populate it.
But there are already set types such as HashSet which is possibly a good match with built in functions for testing for sub sets.
This should get you started:
var input = "#20#30#40";
var hashSetOfNumbers = new HashSet<int>(input
.Split(new []{'#'}, StringSplitOptions.RemoveEmptyEntries)
.Select(s=>int.Parse(s)));
This works for me:
Func<string, string[]> split =
x => x.Split(new [] { '#' }, StringSplitOptions.RemoveEmptyEntries);
if (XAll.Any(x => split(x).Intersect(split(S)).Count() == split(S).Count()))
{
Console.WriteLine("Your String is exist");
}
Now, depending on you you want to handle duplicates, this might even be a better solution:
Func<string, HashSet<string>> split =
x => new HashSet<string>(x.Split(
new [] { '#' },
StringSplitOptions.RemoveEmptyEntries));
if (XAll.Any(x => split(S).IsSubsetOf(split(x))))
{
Console.WriteLine("Your String is exist");
}
This second approach uses pure set theory so it strips duplicates.
I am trying to replace occurrences of a property name with a value in a Dictionary in C#.
I have the following Dictionary:
Dictionary<string, string> properties = new Dictionary<string, string>()
{
{ "property1", #"E:\" },
{ "property2", #"$(property1)\Temp"},
{ "property3", #"$(property2)\AnotherSubFolder"}
};
Where the key is the property name, and the value is just a string value. I basically want to iterate over the values until all set properties have been replaced. The syntax is similar to MSBuild property names.
This should eventually evaluate property 3 to E:\Temp\AnotherSubFolder.
It would help if the RegEx part of the functionality would work, which is where I am stuck on.
I had tried out editing my RegEx on REFiddle here.
The following regex pattern works here:
/\$\(([^)]+)\)/g
Given the text:
$(property2)\AnotherSubFolder
It highlights the $(property2).
However, putting this together in .NET fiddle, I don't get any matches with the following code:
var pattern = #"\$\(([^)]+)\)/g";
Console.WriteLine(Regex.Matches(#"$(property2)AnotherSubFolder", pattern).Count);
Which outputs 0.
I am not too sure why here. Why is my match returning zero results?
.NET should match globally by default.
I'm not aware of support for /g as that is a Perl-ism, so remove it, and the leading /, .NET is trying to match them literally.
Regular Expressions may be overkill here, and may even introduce issues if your properties or values contain special characters, or characters that will be evaluated as regular expressions themselves.
A simple replacement should work:
Dictionary<string, string> properties = new Dictionary<string, string>()
{
{ "property1", #"E:\" },
{ "property2", #"$(property1)\Temp"},
{ "property3", #"$(property2)\AnotherSubFolder"}
};
Dictionary<string, string> newproperties = new Dictionary<string, string>();
// Iterate key value pairs in properties dictionary, evaluate values
foreach ( KeyValuePair<string,string> kvp in properties ) {
string value = kvp.Value;
// Execute replacements on value until no replacements are found
// (Replacement of $(property2) will result in value containing $(property1), must be evaluated again)
bool complete = false;
while (!complete) {
complete = true;
// Look for each replacement token in dictionary value, execute replacement if found
foreach ( string key in properties.Keys ) {
string token = "$(" + key + ")";
if ( value.Contains( token ) ) {
value = value.Replace( "$(" + key + ")", properties[key] );
complete = false;
}
}
}
newproperties[kvp.Key] = value;
}
properties = newproperties;
We have a template URL like:
http://api.example.com/sale?auth_user=xxxxx&auth_pass=xxxxx&networkid={networkid}&category=b2c&country=IT&pageid={pageid}&programid=133&saleid=1&m={master}&optinfo={optinfo}&publisher={publisher}&msisdn={userId}
and I have values for these constant tokens. How can replace all these tokens in C#?
A simple approach is to use a foreach and a Dictionary with a String.Replace:
var values = new Dictionary<string, string> {
{ "{networkid}", "WHEEE!!" }
// etc.
};
var url = "http://api.example.com/sale?auth_user=xxxxx&auth_pass=xxxxx&networkid={networkid}&category=b2c&country=IT&pageid={pageid}&programid=133&saleid=1&m={master}&optinfo={optinfo}&publisher={publisher}&msisdn={userId}";
foreach(var key in values.Keys){
url = url.Replace(key,values[key]);
}
There is no standard way to "replace with dictionary values" in .NET. While there are a number of template engines, it's not very hard to write a small solution for such an operation. Here is an example which runs in LINQPad and utilizes a Regular Expression with a Match Evaluator.
As the result is a URL,
it is the callers responsibility to make sure all the supplied values are correctly encoded. I recommend using Uri.EscapeDataString as appropriate .. but make sure to not double-encode, if it is processed elsewhere.
Additionally, the rules of what to do when no replacement is found should be tailored to need. If not-found replacements should be eliminated entirely along with the query string key, the following can expand the regular expression to #"\w+=({\w+})" to also capture the parameter key in this specific template situation.
string ReplaceUsingDictionary (string src, IDictionary<string, object> replacements) {
return Regex.Replace(src, #"{(\w+)}", (m) => {
object replacement;
var key = m.Groups[1].Value;
if (replacements.TryGetValue(key, out replacement)) {
return Convert.ToString(replacement);
} else {
return m.Groups[0].Value;
}
});
}
void Main()
{
var replacements = new Dictionary<string, object> {
{ "networkid", "WHEEE!!" }
// etc.
};
var src = "http://api.example.com/sale?auth_user=xxxxx&auth_pass=xxxxx&networkid={networkid}&category=b2c&country=IT&pageid={pageid}&programid=133&saleid=1&m={master}&optinfo={optinfo}&publisher={publisher}&msisdn={userId}";
var res = ReplaceUsingDictionary(src, replacements);
// -> "http://api.example.com/sale?..&networkid=WHEEE!!&..&pageid={pageid}&..
res.Dump();
}
More advanced techniques, like reflection and transforms, are possible - but those should be left for the real template engines.
I am guessing you are trying to replace parameters in url with your values. This can be done using C# HttpUtility.ParseQueryString
Get the CurrentURL from
var _myUrl = System.Web.HttpUtility.ParseQueryString(Request.RawUrl);
Read Parameter from your Query string
string value1 = _myUrl ["networkid"];
Write a value into the QueryString object.
_myUrl ["networkid"] = "Your Value";
and then finally turn it back into URL
var _yourURIBuilder= new UriBuilder(_myUrl );
_myUrl = _yourURIBuilder.ToString();
You can use this alos using LinQ
Dictionary<string, string> myVal = new Dictionary<string, string>();
myVal.Add("networkid", "1");
myVal.Add("pageid", "2");
myVal.Add("master", "3");
myVal.Add("optinfo", "4");
myVal.Add("publisher", "5");
myVal.Add("userId", "6");
string url = #"http://api.example.com/sale?auth_user=xxxxx&auth_pass=xxxxx&networkid={networkid}&category=b2c&country=IT&pageid={pageid}&programid=133&saleid=1&m={master}&optinfo={optinfo}&publisher={publisher}&msisdn={userId}";
myVal.Select(a => url = url.Replace(string.Concat("{", a.Key, "}"), a.Value)).ToList();
this line can do your required functionlity
myVal.Select(a => url = url.Replace(string.Concat("{", a.Key, "}"), a.Value)).ToList();
There is a Nuget called StringTokenFormatter that does this well
https://www.nuget.org/packages/StringTokenFormatter/
Regex.Replace makes a single pass over a template string, offering you an opportunity to replace matched expressions. Use it by creating an regular expression that matches any token. Then look up replacement values for the tokens in a dictionary.
static string ReplaceTokens(string template, Dictionary<string, string> replacements) =>
Regex.Replace(template, #"{(\w+)}",
match => replacements.TryGetValue(match.Groups[1].Value, out string replacement) ? replacement : match.Value);
The algorithm completes in time linear with the size of the template string and the replacement strings, so O(t + r). Beware of algorithms that make multiple passes. They run slowly in time O(t * r) and will give incorrect results if one of the replacement values contains a token for later replacement. This unit test shows the pitfall:
public void TestReplaceTokens() {
var replacements = new Dictionary<string, string> {
["Movement"] = "drive {DontReplace}",
["DontReplace"] = "Should not appear"
};
string withReplacements = ReplaceTokens("I always {Movement} in {Direction}.", replacements);
Assert.AreEqual("I always drive {DontReplace} in {Direction}.", withReplacements);
}
I have two arrays that need to be mapped. In code
var result = "[placeholder2] Hello my name is [placeholder1]";
var placeholder = { "[placeholder1]", "[placeholder2]", "[placeholder3]", "[placeholder4]" };
var placeholderValue = { "placeholderValue3", "placeholderValue2", "placeholderValue3" };
Array.ForEach(placeholder , i => result = result.Replace(i, placeholderValue));
given i, placeholderValue needs to be set in an intelligent way. I can implement a switch statement. The cyclomatic complexity would be unacceptable with 30 elements or so. What is a good pattern, extension method or otherwise means to achieve my goal?
I skipped null checks for simplicity
string result = "[placeholder2] Hello my name is [placeholder1]";
var placeHolders = new Dictionary<string, string>() {
{ "placeholder1", "placeholderValue1" },
{ "placeholder2", "placeholderValue2" }
};
var newResult = Regex.Replace(result,#"\[(.+?)\]",m=>placeHolders[m.Groups[1].Value]);
The smallest code change would be to just use a for loop, rather than a ForEach or, in your case, a ForEach taking a lambda. With a for loop you'll have the index of the appropriate value in the placehoderValue array.
The next improvement would be to make a single array of an object holding both a placeholder and it's value, rather than two 'parallel' arrays that you need to keep in sync.
Even better than that, and also even simpler to implement, is to just have a Dictionary with the key being a placeholder and the value being the placeholder value. This essentially does the above suggestion for you through the use of the KeyValuePair class (so you don't need to make your own).
At that point the pseudocode becomes:
foreach(key in placeholderDictionary) replace key with placeholderDictionary[key]
I think you want to use Zip to combine the placeholders with their values.
var result = "[placeholder2] Hello my name is [placeholder1]";
var placeholder = new[] { "[placeholder1]", "[placeholder2]", "[placeholder3]", "[placeholder4]" };
var placeholderValue = new[] { "placeholderValue1", "placeholderValue2", "placeholderValue3", "placeholderValue4" };
var placeHolderPairs = placeholder.Zip(placeholderValue, Tuple.Create);
foreach (var pair in placeHolderPairs)
{
result = result.Replace(pair.Item1, pair.Item2);
}