The meaning of ref and out in C # and how to use it

The meaning and use of ref and out in the original C #

When passing an argument to a method, the corresponding shape delegate is initialized with a copy of the argument , regardless of whether the formal parameter is a value type (for example, int), a nullable type (int?), or a reference type , which is true. That is, whatever changes are made inside the method without affecting the value of the argument. For example, for a reference type, a change to a method simply alters the referenced data, but the argument itself does not change, and it still references the same object.

The code is as follows:

    Using System;      Using System.Collections.Generic;      Using System.Linq;      Using System.Text;            Namespace Ref_out      {          class program          {              static void Main (string[] args)              {                  int i = 8;                  Console.WriteLine (i);                  Doincrease (i);                  Console.WriteLine (i);              }                    static void Doincrease (int a)              {                  a++;              }          }      }  

The results of the operation are as follows:

If you use the REF keyword, any actions applied to the parameter apply to the argument as well, because the parameters and arguments refer to the same object.

PS: Both the argument and the parameter must be prefixed with the REF keyword appended.

    Using System;      Using System.Collections.Generic;      Using System.Linq;      Using System.Text;            Namespace Ref_out      {          class program          {              static void Main (string[] args)              {                  int i = 8;                  Console.WriteLine (i);   8                  doincrease (ref i);      Ref                  Console.WriteLine (i) must also be added before the argument.   The 9//ref keyword causes the action on the parameter to be applied to the argument              }                    static void Doincrease (ref int a)   //parameter must be ref              {                  a++;              }          }      }  

The operation results are as follows

The ref argument must also be initialized before it is used , or it cannot be compiled.

    Using System;      Using System.Collections.Generic;      Using System.Linq;      Using System.Text;            Namespace Ref_out      {          class program          {              static void Main (string[] args)              {                  int i;          The ref argument is not initialized, so the program cannot compile                  Console.WriteLine (i);                  Doincrease (ref i);                  Console.WriteLine (i);              }                    static void Doincrease (ref int a)              {                  a++;              }          }      }  

Sometimes we want the parameters to be initialized by the method itself , when the out parameter can be used.

The code is as follows:

    Using System;      Using System.Collections.Generic;      Using System.Linq;      Using System.Text;            Namespace Ref_out      {          class program          {              static void Main (string[] args)              {                  int i;    No initialization                  //console.writeline (i);//Here I uninitialized, compile error                  doincrease (out i);  The method is used to assign the initial value to the argument                  Console.WriteLine (i);              }                    static void Doincrease (out int a)              {                  a = 8;  Initialize the a++ in the method                  ;    A = 9              }          }        

The meaning of ref and out in C # and how to use it