C # learning notes-methods and parameter Modifiers

I. Learning Content

Construct various details of the C # method;

Out, ref, and Params keywords;

. Net 4 introduces new features: optional parameters and naming parameters.

 

2. Parameter modifiers of methods

1. No Modifier

If a method parameter is not marked with a parameter modifier, it will be passed by value, which means that the called method will get a copy of it.

This is the most common and common parameter tag form.

 

2. Out Modifier

When an out parameter is used to modify a parameter, this parameter is equivalent to the output parameter of this method;

It is passed by reference rather than by value;

The called method must be assigned a value for this parameter; otherwise, an error is reported during compilation;

When calling a method with the out parameter, the out modifier must also be used;

When you call a method with the out parameter, you can assign a value to the parameter first, because the called method will assign a value to it;

Its most important application is that multiple values can be returned in a method.

 

3. Ref Modifier

This is a method for passing values by reference ';

If you want the parameter passed to the called method to change the value in the method instead of a copy, you can declare the parameter as REF;

This parameter must have been assigned a value before calling the method, which is different from the out modifier;

 

4. Params Modifier

Pass the variable number of parameters (these parameters should be of the same type) as a single logical parameter to the method, similar to an array;

In the called method, Params parameters should be treated as an array, and zero input parameters are supported;

A Method supports up to one Params parameter, and must be the last parameter in the parameter list;

This technology facilitates callers.

 

Iii. New Features of. Net 4

1. Optional parameters

That is, only a parameter has specified a default value in the method declaration;

The value of the optional parameter must be determined at compilation, but cannot be determined at runtime; otherwise, an error is returned during compilation;

If an optional parameter is placed before a non-optional parameter, an error is reported during compilation.

 

2. Named Parameters

Parameter values can be specified in any order when a method is called;

During the call process, the named parameters must be placed at the end of the method call;

Optional parameters are often used with named parameters;

 

Optional and named parameters are supported mainly to simplify the interoperability with COM.

 

Member overloading:

Make sure that each method has a different parameter group: The number or type is different, but the members of different return types are not unique enough to meet the conditions.