Transfer from Pnljs delegate (func<int,bool>)

Often see Func<int, bool> This way of writing, see This is no mind to look down. We still need to be quiet when we learn technology.

The Func to func<int,bool> goes to the definition to see its explanation:

//Summary:
   //     Encapsulates a method that has one parameter and returns the type value specified by the TResult parameter.
   //
   //Parameters:
   //   arg:
    //     The parameters of the method encapsulated by this delegate.
   //
   //Type parameters:
   //   T:
    //     The parameter type of the method encapsulated by this delegate.
   //
   //   TResult:
   //      The return value type of the method encapsulated by this delegate.
   //
   //Return results:
   //     The return value of the method encapsulated by this delegate.
    [Typeforwardedfrom ("System.core, version=3.5.0.0, Culture=neutral, publickeytoken= b77a5c561934e089 ")]
    public delegate TResult Func<in T, out tresult> (t arg);

In t represents the input parameter 1 out TResult represents the output parameter 2 again see the return value is TResult 3 constructor method required parameter is T 4

1 Compare with 4,2 and 3, what did you find?!         Parameter type, right. 5

Func is a delegate, the delegate can be stored inside the method, then we have to build a matching method: Take func<int,bool> as an example:

private bool IsNumberLessThen5 (int number)

{return number < 5;}

Func<int,bool> f1 = IsNUmberLessThen5;

Call: BOOL flag= F1 (4);

Here is the specific code:

Using System; Using System.Collections.Generic; Using System.Linq; Using System.Linq.Expressions; Using System.Text; Using System.Threading.Tasks;

Namespace ConsoleApplication1 {class Program {static void Main (string[] args) {Func             <int, bool> f1 = IsNumberLessThen5;             BOOL flag = f1 (4); Console.WriteLine (flag);

           //The following are other uses, similar to the ISNUMBERLESSTHEN5 function. It's just a different notation.             func<int, bool> f2 = i = i < 5;             func<int, bool> f3 = (i) + = {return I < 5 ; };             Func<int, bool> f4 = delegate (int i) {return I < 5; };             flag = F2 (4); Console.WriteLine (flag);             flag = F3 (4); Console.WriteLine (flag);             flag = f4 (4); Console.WriteLine (flag);            

Console.ReadLine (); }

private static bool IsNumberLessThen5 (int number) {if (number < 5) return true;         return false; }     } }

Transfer from Pnljs delegate (func<int,bool>)