How to Retrieve Output Parameters from a Stored Procedure in C#?

Retrieving Output Parameters from Stored Procedures in C#

Many database interactions utilize stored procedures to efficiently manage data. A common requirement is retrieving output parameters, especially when dealing with automatically generated primary keys. This example demonstrates how to correctly handle output parameters in C# when working with SQL Server stored procedures.

The problem often arises when trying to capture the newly generated primary key after an INSERT operation. The following modified stored procedure provides a solution:

CREATE PROCEDURE usp_InsertContract
(
  @ContractNumber varchar(7),
  @NewId int OUTPUT
)
AS
BEGIN
  INSERT INTO [dbo].[Contracts] (ContractNumber)
  VALUES (@ContractNumber);

  SELECT @NewId = SCOPE_IDENTITY();
END;

This stored procedure accepts a contract number and returns the newly generated ID via the @NewId output parameter using SCOPE_IDENTITY().

Here's the updated C# code to retrieve this output parameter:

// Establish database connection and command object
using (SqlConnection conn = new SqlConnection(pvConnectionString))
using (SqlCommand cmd = new SqlCommand("dbo.usp_InsertContract", conn))
{
  cmd.CommandType = CommandType.StoredProcedure;

  // Define and add parameters
  cmd.Parameters.AddWithValue("@ContractNumber", contractNumber);
  cmd.Parameters.Add("@NewId", SqlDbType.Int).Direction = ParameterDirection.Output;

  // Open connection and execute the stored procedure
  conn.Open();
  cmd.ExecuteNonQuery();

  // Retrieve the output parameter value
  int contractID = Convert.ToInt32(cmd.Parameters["@NewId"].Value);
  conn.Close();
}

This C# code connects to the database, executes the stored procedure, and efficiently retrieves the @NewId output parameter, storing it in the contractID variable. The newly generated primary key is now available for further processing within your application.

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