Delete a row from a table, specified by the user, with the click of a button in C#

Question

I am using Visual Studio 2019 Winforms C# .NET Framework and in the Winforms project, there is a textbox and a button.

When I type a parameter name in the textbox and click the button, I want to delete the row from the table called "Serial_Key".

private void button1_Click(object sender, EventArgs e)
{
    string mainconn = ConfigurationManager.ConnectionStrings["Myconnection"].ConnectionString;
    SqlConnection sqlconn2 = new SqlConnection(mainconn);
    string sqlquery = "select * from [dbo].[Serial-Keys] where Serial_Key=@Serial_Key";
    sqlconn2.Open();
    SqlCommand sqlcomm = new SqlCommand(sqlquery, sqlconn2);
    sqlcomm.Parameters.AddWithValue("@Serial_Key", SerialKeyBox.Text);
    SqlDataAdapter sda = new SqlDataAdapter(sqlcomm);
    DataTable dt = new DataTable();
    sda.Fill(dt);
    sqlcomm.ExecuteNonQuery();
    if (dt.Rows.Count > 0)
    {
        Cursor.Current = Cursors.WaitCursor;
        try
        {
            
        }
        catch (Exception)
        {

        }
        Cursor.Current = Cursors.Default;
    }
    else
    {
        MessageBox.Show("Invalid Serial Key!");
        label7.Text = "Serial Key Rejected...";
    }
}

@TERIZOROGAME Seems like you already have some solution. But we don't know what's the issue you are facing with the current solution. So not sure what's the solution you are looking for. — Chetan, Jul 30 '20 at 04:56

score 1 · Accepted Answer · answered Jul 30 '20 at 04:55

Change your select statement to a delete statement and remove all the DataAdaptor stuff as thats only required if you are querying records.

private void button1_Click(object sender, EventArgs e)
{
    string mainconn = ConfigurationManager.ConnectionStrings["Myconnection"].ConnectionString;
    SqlConnection sqlconn2 = new SqlConnection(mainconn);
    // Use a Delete statement, not a select
    string sqlquery = "delete from [dbo].[Serial-Keys] where Serial_Key = @Serial_Key";
    sqlconn2.Open();
    SqlCommand sqlcomm = new SqlCommand(sqlquery, sqlconn2);
    // Construct the parameter yourself with the correct datatype and precision
    sqlcomm.Parameters.Add(new SqlParameter("@Serial_Key", SqlDbType.VarChar, 32) { Value = SerialKeyBox.Text });
    // Remove all the DataAdaptor stuff
    // ExecuteNonQuery returns the rows affected
    int numberOfRecords = sqlcomm.ExecuteNonQuery();
    if (numberOfRecords > 0)
    {
        // Any code to run on an effective delete
    }
    else
    {
        MessageBox.Show("Invalid Serial Key!");
        label7.Text = "Serial Key Rejected...";
    }
}

I upvoted it but it's not shown because I'm not 15+ rep. – TERIHAX Aug 02 '20 at 06:06 — TERIHAX, Aug 02 '20 at 06:06

score 1 · Answer 2 · answered Jul 30 '20 at 05:58

1

If you install Dapper then your code becomes very simple:

private async void button1_Click(object sender, EventArgs e)
{
  using(var c = new SqlConnection(_connStr))
    await c.ExecuteAsync("DELETE FROM dbo.[Serial-Keys] WHERE serial_key = @sk", new { sk = SerialKeyBox.Text });
}

And, bonus, it doesn't jam your UI while it runs queries

I recommend you put that string mainconn = ConfigurationManager.ConnectionStrings["Myconnection"].ConnectionString; into a class level variable called _connStr instead, to help tidy things up

http://dapper-tutorial.net (no affiliation)

answered Jul 30 '20 at 05:58

Caius Jard

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the problem is I don't want any DLL files with it. But anyway `@Dale K` fixed my problem. – TERIHAX Aug 01 '20 at 08:39
"I don't want any DLL files with it" - better not use .net framework then; need to start work on writing everything from scratch, database drivers, graphics drivers, the lot because you're using System.Data.dll right now even... Or, [embed the DLLs into the EXE](https://stackoverflow.com/questions/189549/embedding-dlls-in-a-compiled-executable) if you're looking for some way of creating a self contained single exe, but want to leverage code that is already written – Caius Jard Aug 01 '20 at 08:51
`@Caius Jard` Like I mean no third-party dlls. ONLY microsoft – TERIHAX Aug 01 '20 at 13:01
Because Microsoft never use third party DLLs? – Caius Jard Aug 01 '20 at 14:13
I mean the built-in dlls – TERIHAX Aug 02 '20 at 06:05

Delete a row from a table, specified by the user, with the click of a button in C#

2 Answers2