使用C＃WPF和SQL添加行时的自动增量值

Question

I'm working with C# WPF in Visual Studio Express 2012. I've created a local service-based database ( .mdf database).

I've created a table with

    CREATE TABLE [dbo].[Scenes] (
         [id]              INT           IDENTITY (1, 1) NOT NULL,
         [Planning_period] NVARCHAR (50) NOT NULL,
         [Scene_name]      NVARCHAR (50) NOT NULL,
         PRIMARY KEY CLUSTERED ([id] ASC)
    );

I want to be able to add a new row but the following code doesn't work because I'm leaving id as null. How do I get it to increment automatically when I add data?

    SqlConnection cn = new SqlConnection(global::WaterfowlModel.Properties.Settings.Default.WAMConnectionString);
    try
    {
        string sql = "INSERT INTO Scenes (Planning_period, Scene_name) Values ('" + working_plan + "','" + Create_plan_txt.Text +"')";
        SqlCommand cmd = new SqlCommand(sql, cn);
        cn.Open();
        cmd.ExecuteNonQuery();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message, "Error", MessageBoxButton.OK);
    }
    finally
    {
        cn.Close();
    }

Thanks!

EDIT

I've attempted this with a stored procedure as well and received the same error.

CREATE PROCEDURE [dbo].[Add_Scene]
    @param1 nvarchar(50),
    @param2 nvarchar(50)
AS
    INSERT INTO Scenes(Planning_period, Scene_name)
    VALUES(@param1, @param2)

and code:

        string sql = "Add_Scene";
        SqlCommand cmd = new SqlCommand(sql, cn);
        SqlParameter planname = new SqlParameter("@param1", working_plan);
        SqlParameter scenename = new SqlParameter("@param2", Create_plan_txt.Text);

        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add(planname);
        cmd.Parameters.Add(scenename);
        cn.Open();
        cmd.ExecuteNonQuery();

Answer 1

First you should be carefull using that code, you should user parameters for the sqlCommand, and not made a concatenation...

Second to work with the database you should see how to make the call, not using the sql Insert statement, but calling a stored procedure, that insert the record on the table, and holds the Insert statement.

So resuming, if you see how to do what I answered you, you'll see that once you have the stored procedure working fine, you will be able to made the auto increment without worries ;).

And you win in all, because you code will be more robust, secure and reliable.

Greetings.

Answer 2

I followed instructions found Create stored procedure to add with auto increment as its primary field?

One thing I had to do was rebuild the solution before Starting the application. Before I rebuilt it didn't work.

Answer 3

With the change you have made, you just need to return the ID in the Stored Procedure after the Insert, you have cupple of ways to do that, but be carefull...

If you do not have lots of traffic in your database you can use just this, is more faster:

CREATE PROCEDURE [dbo].[Add_Scene]
    @param1 nvarchar(50),
    @param2 nvarchar(50)
AS
BEGIN
    INSERT INTO Scenes(Planning_period, Scene_name)
    VALUES(@param1, @param2)

    RETURN @@IDENTITY
END

This is a standard for this type of Stored Procedure, as you can see here: http://technet.microsoft.com/en-us/library/ms187342.aspx . However this function may not return the correct value, if you are working in a environment with lots of database traffic, it just return the ID of the last Insert operation, if there is concurrency, you may have problems, so check for other options, that may be slower in execution but more reliable.

The main point is to return from the database the ID auto incremented, after the insert, so you can read the value of the insert you made.

Hope that this helps you.

Greetings.