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This article mainly explains "what are the C# parameters". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the C# parameters"?

Simple types (such as int,double,char), enum types, and struct types are all value types.

Class types, interface types, delegate types, and array types are all reference types.

1. Value parameter (Value parameters)

By default, parameters are value parameters.

Void Foo (StringBuilder x) {x = null;}... StringBuilder y = new StringBuilder (); y.Append ("hello"); Foo (y); Console.WriteLine (y==null)

The output is False. Because it is in the form of value transfer, although x is set to null, the value of y does not change. It is important to note, however, that reference type variables hold references, and if two reference type variables refer to the same object, modifications to the object are bound to affect the two reference type variables, as follows:

Void Foo (StringBuilder x) {x.Append ("world");}. StringBuilder y = new StringBuilder (); y.Append ("hello"); Foo (y); Console.WriteLine (y)

The output is hello world. Because after calling the Foo method, the content of the StringBuilder object referenced by y is changed to "hello world", which is achieved by calling the Append method to add "world" through the x reference in the Foo method.

2. Reference parameters (Reference parameters)

The reference parameter does not pass the value of the variable in the function member call, but the variable itself. This means that it does not allocate new memory space for variables in function member declarations, but uses the same storage space as arguments, so the values of arguments and parameters are the same at all times. To use reference parameters in C #, you must explicitly use the keyword ref in both function declarations and function calls, so that it is clear to the code that reference parameters are used.

Void Foo (ref StringBuilder x) {x = null;}. StringBuilder y = new StringBuilder (); y.Append ("hello"); Foo (ref y); Console.WriteLine (y==null)

The output is True. The reference parameter is used here, passing a reference to y (reference), not the value in y (object reference). So the change in the value of parameter x is immediately reflected in y. After the Foo method is called, the value of y is also null.

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