Question

The system I am currently working on uses Stored Procedures for all data access. I’m looking into Dapper at the moment (so far it looks great) but I was wondering if I can use a DynamicParameters object created using a Template but make one of the parameters an output param. For example:

SP:

CREATE PROCEDURE InsertPerson
  @ID int Output,
  @Name varchar(100),
  @DOB DateTime2
AS
--INSERT STATEMENT

SET @ID = SCOPE_IDENTITY()

POCO:

internal class Person
{
  public int ID { get; set; }
  public string Name { get; set; }
  public DateTime DOB { get; set; }
}

Code:

var procParams = new DynamicParameters(person);
connection.Execute("InsertPerson", procParams, commandType: CommandType.StoredProcedure);

// This is where i'm having the issue, can it be done?
person.ID = procParams.Get<int>("ID");

Current I receive an error because the key was not found. Is there a way to get the ID output parameter without manually setting up all of the stored procs parameters?

Answer 1

With a quick tweak, Add now replaces the value from a template, allowing:

public void TestProcWithOutParameter()
{
    connection.Execute(
        @"CREATE PROCEDURE #TestProcWithOutParameter
@ID int output,
@Foo varchar(100),
@Bar int
AS
SET @ID = @Bar + LEN(@Foo)");
    var obj = new
    { // this could be a Person instance etc
        ID = 0,
        Foo = "abc",
        Bar = 4
    };
    var args = new DynamicParameters(obj);
    args.Add("ID", 0, direction: ParameterDirection.Output);
    connection.Execute("#TestProcWithOutParameter", args,
                 commandType: CommandType.StoredProcedure);
    args.Get<int>("ID").IsEqualTo(7);
}

Is that close enough? You can also use ParameterDirection.ReturnValue, of either a pre-existing value or a new value. Note it does not update directly back into the original template; the value must be fetched from the DynamicParameters instance (as shown).