Generic delegated Learning (func and action)

Func <tparams, tresult>

Generic delegation. Tparams is the parameter type of the method encapsulated by this delegate. It can have 0 or more but cannot exceed 4 tresult return value types.

You can use this delegate to indicate a method that can be passed as a parameter without explicitly declaring a custom delegate. This method must correspond to the method signature defined by this delegate. That is to say, the encapsulated method must have a parameter passed to it through a value and must return a value.

Example 1:

Static void main (string [] ARGs)
{

Func <string, string> functest = demo;

Console. writeline (functest ("aaaaaa "));

}

Static string demo (string S)
{
Return S. toupper ();
}

// Output aaaaaa

This delegate can also be used with anonymous methods!

Example 2:

Func <string, string> funtest = delegate (string s) {return S. toupper ();};

Console. writeline (functest ("aaaaaa "));

The output result is the same as that in Example 1.

 

You can also assign a Lambda expressionFuncDelegate

Example 3

 

Func <string, string> functest = s => S. toupper ();

Console. writeline (functest ("aaaaaa "));

 

The output results are the same. Lambda expressions are more concise.

 

But what if there is no return value? Because the func delegate must have a return value, you need to use action.

Action <tparams>

This delegate method has no return value. The tparams parameter type list can only be 1 to 4

Example:

Static void main (string [] ARGs)
{

Action <string> actiontest = demo2;
Actiontest ("Zhang ");

}

Static void demo2 (string S)
{
Console. writeline (S. toupper ());
}

Output Zhang

(Action cannot be used with Lambda expressions like func)