Passing Output parameters to stored procedure using dapper in c# code

Question

I have a stored procedure in this format

CREATE PROCEDURE SP_MYTESTpROC
    @VAR1 VARCHAR(10),
    @VAR2 VARCHAR(20),
    @BASEID INT ,
    @NEWID INT OUTPUT
As Begin
   INSERT INTO TABLE_NAME(username, firstname)
      select @VAR1, @VAR2 
      WHERE ID = @BASEID

   SET @NEWID = SCOPE_IDENTITY() AS INT
END

I am calling this stored procedure from C# code using dapper. My question is: how do I pass in the output parameter to the stored procedure while using dapper?

Answer 1

Just searching the Test.cs file you could find this example

public void TestProcSupport()
{
    var p = new DynamicParameters();
    p.Add("a", 11);
    p.Add("b", dbType: DbType.Int32, direction: ParameterDirection.Output);
    p.Add("c", dbType: DbType.Int32, direction: ParameterDirection.ReturnValue);
    connection.Execute(@"create proc #TestProc 
                         @a int,
                         @b int output
                         as 
                         begin
                             set @b = 999
                             select 1111
                             return @a
                         end");
    connection.Query<int>("#TestProc", p, commandType: CommandType.StoredProcedure).First().IsEqualTo(1111);
    p.Get<int>("c").IsEqualTo(11);
    p.Get<int>("b").IsEqualTo(999);
}

So, I suppose that your C# code could be written as

public void InsertData()
{
    var p = new DynamicParameters();
    p.Add("VAR1", "John");
    p.Add("VAR2", "McEnroe");
    p.Add("BASEID", 1);
    p.Add("NEWID", dbType: DbType.Int32, direction: ParameterDirection.Output);
    connection.Query<int>("SP_MYTESTpROC", p, commandType: CommandType.StoredProcedure);
    int newID =  p.Get<int>("NEWID");
}

As a side note, do not use SP as prefix for your stored procedure. It is reserved for system defined procedures and you could find yourself in troubles if Microsoft decides to use the same name. Albeit improbable it is a bad practice and why risk?