Delegate as function

Question

Below function working ok but I want to make it simple.

if (list.Exists(delegate(string s) { return s.Contains(str); })) { string name = list.Find(delegate(string s) { return s.Contains(str); }); }

I am using delegate(string s) { return s.Contains(str); } two times Is there any way to make this simple. I know how to create delegate but don't know how to use it.

 //create delegate public delegate bool nameExistsDelegate(List<string> list, string name); // Create a method for a delegate. public static bool IsnameExists(List<string> list, string name) { return list.Exists(delegate(string s) { return s.Contains(name) ; }); } // Create a method for a delegate. public static string GetName(List<string> list, string name) { return list.Find(delegate(string s) { return s.Contains(name) ; }); }

UPDATE

stuck with .NET 2.0 so I can't use LINQ

Ani · Accepted Answer · 2010-10-21 03:04:29Z

The anonymous method you're using will be converted to a Predicate<string> delegate by the compiler. With this in mind, you can introduce a local to get rid of the redundancy you don't want.

Predicate<string> containsStr = delegate(string s) { return s.Contains(str); }; if (list.Exists(containsStr)) { string name = list.Find(containsStr); ... }

In C# 3.0 or later, you can express this even more succintly with lambda-expressions.

Predicate<string> containsStr = s => s.Contains(str);

On another note, you don't need to first test that str exists and then proceed to find it (assuming the list doesn't contain nulls), you could just do:

string name = list.Find(s => s.Contains(str)); if(name != null) { //found }

Of course, I should also point out that strings don't contain any extra meta-data other than the characters present in them, so you don't gain anything by 'finding' a string in a list over just proving it exists (unless you meantFindIndex).

Preet Sangha · Accepted Answer · 2010-10-21 02:35:21Z

if you're on .net 3.5 you can use lamdas

 //create delegate public delegate bool nameExistsDelegate(List<string> list, string name); static Func<string, bool> exists = s => return s.Contains(name); // Create a method for a delegate. public static bool IsnameExists(List<string> list, string name) { return list.Exists(s => exists(s)); } // Create a method for a delegate. public static string GetName(List<string> list, string name) { return list.Find(s => exists(s)); }

Gishu · Accepted Answer · 2010-10-21 02:51:11Z

I'd recommend reading up on the standard delegate types in C#

Here you actually need a Predicate, which takes in an object, tests it with some condition and returns a pass/fail result.

Predicate<string> containsCheck = item = > item.Contains(str); if (list.Exists(containsCheck) { string name = list.Find(containsCheck); }

Note: all of the code can also be done using LINQ, which is considerable simpler. But I guess you must be learning delegates right now.. JFYI

using System.Linq; ... Predicate<string> substringCheck = item => item.Contains(str); var exists = list.Any(substringCheck); var getMatch = list.First(substringCheck);

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