c# database listbox item remove

Question

I making a database and I can add names, but I can't remove please help me.

This is my code:

private void button2_Click(object sender, EventArgs e)
{
    using (connection = new SqlConnection(connectionString))
    using (SqlCommand cmds = new SqlCommand("DELETE FROM Recipe WHERE firstName = @user", connection))
    {
        connection.Open();
        cmds.Parameters.AddWithValue("@user", cmds);
        cmds.ExecuteNonQuery();

    }
    populateRecipe();
}

This is the error

An unhandled exception of type System.ArgumentException occurred in System.Data.dll Additional information: No mapping exists from object type System.Data.SqlClient.SqlCommand to a known managed provider native type.

An unhandled exception of type 'System.ArgumentException' occurred in System.Data.dll Additional information: No mapping exists from object type System.Data.SqlClient.SqlCommand to a known managed provider native type. — Captain, Aug 30 '15 at 07:25
I have read here http://stackoverflow.com/questions/9155004/difference-with-parameters-add-and-parameters-addwithvalue/9155103#9155103 that `cmds.Parameters.AddWithValue` is not a good way for work. It only send a `nvarchar` to the database instead of an `int`. — H. Pauwelyn, Aug 30 '15 at 07:29

score 3 · Answer 1 · answered Aug 30 '15 at 07:16

3

Instead of passing the cmds itself to the AddWithValue method :

cmds.Parameters.AddWithValue("@user", cmds);

I suppose you should pass your actual uesrname :

cmds.Parameters.AddWithValue("@user", username);

answered Aug 30 '15 at 07:16

Mohammad Chamanpara

2,049
1
15
23

im done learning c# now i need to continue SQL Learning CREATE TABLE [dbo].[Recipe] ( [Id] INT IDENTITY (1, 1) NOT NULL, [firstName] NVARCHAR (50) NOT NULL, PRIMARY KEY CLUSTERED ([Id] ASC) ); it's my database – Captain Aug 30 '15 at 07:22
@Captain I suggest you learning Entity Framework. It's not only pretty easy to use but you will also enjoy dealing with it. Good luck. – Mohammad Chamanpara Aug 30 '15 at 07:28

score 1 · Answer 2 · answered Aug 30 '15 at 07:15

You are passing the cmds variable as the value for the @user parameter which doesn't make sense because it's a SqlCommand object:

cmds.Parameters.AddWithValue("@user", cmds);

Don't you intend to pass the user's name that you want to delete instead?

cmds.Parameters.AddWithValue("@user", "Username");

c# database listbox item remove

2 Answers2