In C # and SQL ref and out of output

When you will need to use the ref and out

1. Sometimes we need to get a value in the method of running the state, according to the methods defined, we can only get a return value, but sometimes we might want to get more value, can not be returned by the return value of such information, we can use ref or out parameters before, to obtain a plurality of return value.
2. Sql stored in the implementation process, we can state by running the sql statement in a stored procedure returns the corresponding value of return .sql only supports Int return value format, we can get multiple return values ​​by using the ref or out, and presented to a page

What is the difference between ref and out:

When the runtime code in the method, need to use the parameters and return values ​​required by this parameter, we need to use ref.

If only to get multiple return values, and when they do not need to use these methods parameters, we can use out.

Examples

Example 1: Using ref and out pages asp.net

protected  void the Page_Load ( Object SENDER, EventArgs E) 
{ 
    String str1, str2, S1 = " first parameter " , S2 = " second parameter " ; 

    // run the following line of code will be prompted with the following error:
     //   use unassigned local variable "str1"
     // UseRef (str1 REF, REF str2); 

    // output:
     //   first parameter out is
     //   used out of the second parameter 
    UseOut ( out str1, out str2) ; 
    Response.Write (str1 + " a " ); 
    Response.Write (str2 +" A " ); 

    // output:
     //   first parameter REF
     //   second parameter REF 
    UseRef ( REF S1, REF S2); 
    Response.Write (S1 + " a " ); 
    Response.Write (S2 + " a " ); 
} 

public  void UseOut ( out  String str1, out  String str2) 
{ 
    str1 = " used out of the first parameter " ; 
    str2 = "Out of the second parameter " ; 
} 

public  void UseRef ( REF  String S1, REF  String S2) 
{ 
    S1 + = " Use REF " ; 
    S2 + = " Use REF " ; 
}

Example 2: Process parameters stored using the output keyword corresponds to c # code, then is ref and out.

ref and out and output relationship is as follows:

ParameterDirection Value	description	The corresponding C #	The corresponding SQL
Input	Entry
InputOutput	input Output	ref	The corresponding output
Output	Export	out
ReturnValue	return value

Start example:

The establishment of the Employee table:

Data in the table below:

Build stored procedures as follows:

    ALTER PROCEDURE dbo.InsertEmployee
    (
        @EmployeeName nvarchar(20),
        @EmployeeAge int=null,
        @EmployeeDepartmentID int=null,
        @EmployeeScore int=null,
        @outValue nvarchar(20) output
    )

    AS
        /* SET NOCOUNT ON */
        if exists(select * from Employee where EmployeeName=@EmployeeName)
        begin
            set @outValue='用户名'+@EmployeeName+'重复!'
            return
        end
        
        insert into Employee (EmployeeName,EmployeeAge,EmployeeDeparmentID,EmployeeScore)
        values (@EmployeeName,@EmployeeAge,@EmployeeDepartmentID,@EmployeeScore)
        
        set @outValue='用户'+@EmployeeName+'建立成功!'
        
        return

Page code is as follows:

string connectionString = ConfigurationManager.ConnectionStrings["dbstconnectionstring"].ConnectionString;

SqlConnection conn = new SqlConnection(connectionString);

SqlCommand cmd = conn.CreateCommand();

cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "InsertEmployee";

cmd.Parameters.AddWithValue("@EmployeeName", "宋八");
cmd.Parameters.AddWithValue("@EmployeeAge", 20 is ); 
cmd.Parameters.AddWithValue ( " @EmployeeDepartmentID " , . 1 ); 
cmd.Parameters.AddWithValue ( " @EmployeeScore " , 95 ); 

// Note param_outValue.Direction
 //       set param_outValue.Direction = Output, parameter need only be statement to
 //       the corresponding database Output
 // the SqlParameter = new new param_outValue the SqlParameter ( "@ outValue", SqlDbType.NVarChar, 20 is);
 // param_outValue.Direction = ParameterDirection.Output;
 // cmd.Parameters.Add (param_outValue);    

// Note param_outValue.Direction
 //      Set param_outValue.Direction = InputOutput, parameters need to be initialized
 //       in the corresponding database Output 
the SqlParameter param_outValue = new new the SqlParameter ( " @outValue " , SqlDbType.NVarChar, 20 is ); 
param_outValue.Direction = ParameterDirection.InputOutput; 
param_outValue.Value = String . Empty; 
cmd.Parameters.Add (param_outValue);   

conn.Open (); 
the cmd.ExecuteNonQuery (); 
conn.Close (); 

Response.Write (param_outValue.Value);

The first time you run the output:

Song eight users build successful! 

Second run output:

Username Song eight repeat!

 

This switched: https: //www.cnblogs.com/oneword/archive/2010/07/29/1787569.html