How Can I Retrieve Output Parameters, Including SCOPE_IDENTITY(), from SQL Server Stored Procedures in C#?

Accessing Output Parameters from SQL Server Stored Procedures within C# Applications

The Challenge

Successfully retrieving output parameter values, particularly the primary key using SCOPE_IDENTITY(), from SQL Server stored procedures in C# can be tricky. This article addresses common difficulties and provides a practical solution.

Stored Procedure Example

The usp_InsertContract stored procedure demonstrates the process. It inserts a record into the Contracts table and returns the newly generated primary key (the Id column) via the @NewId output parameter. The updated procedure uses SCOPE_IDENTITY() for accurate primary key retrieval:

<code class="language-sql">CREATE PROCEDURE usp_InsertContract
    @ContractNumber varchar(7),
    @NewId int OUTPUT
AS
BEGIN
    INSERT INTO [dbo].[Contracts] (ContractNumber)
    VALUES (@ContractNumber);

    SELECT @NewId = SCOPE_IDENTITY();
END;</code>

C# Implementation

The C# code snippet below shows how to handle the output parameter:

<code class="language-csharp">SqlParameter pvNewId = new SqlParameter();
pvNewId.ParameterName = "@NewId";
pvNewId.DbType = DbType.Int32;
pvNewId.Direction = ParameterDirection.Output;

// ... (Add pvNewId to the SqlCommand object 'cmd') ...

// Execute the stored procedure
cmd.ExecuteNonQuery();

// Retrieve the output value
int contractID = Convert.ToInt32(cmd.Parameters["@NewId"].Value);</code>

Common Pitfalls and Solutions

If you're encountering issues, verify the following:

• Identity Column: Confirm that your Contracts table includes an identity column (auto-incrementing primary key).
• SCOPE_IDENTITY() Usage: Ensure correct use of SCOPE_IDENTITY() within the stored procedure to retrieve the last inserted identity value.
• Parameter Configuration: Double-check that the SqlParameter object (pvNewId) is correctly added to the SqlCommand object (cmd) and that its properties (ParameterName, DbType, Direction) are accurately set.

By addressing these points, you can effectively retrieve output parameters, including those generated by SCOPE_IDENTITY(), from your SQL Server stored procedures within your C# applications.

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