Command.Parameters.Add not working? C#

Question

I'm trying to figure out what is going on with my code and I can't figure it out. I'm trying to query a db to find out information where a user previously selected a variable.

The problem I'm running into is that it never replaces the @client with the value in the Parameters.AddWithValue method. I'm just not sure what I'm doing wrong.

selClient = comboBox1.SelectedItem.ToString();
string cmdText = "Select [Tax EIN] From [TblClientInfo] Where [Client Name] = '@client';";

using (var conn = new SqlConnection("connection info"))
{
    SqlCommand cmd2 = new SqlCommand(cmdText, conn);
    {
        cmd2.Parameters.AddWithValue("@client", selClient);
        try
        {
            conn.Open();
            SqlDataReader rd = cmd2.ExecuteReader();
            while (rd.Read())
            {
                MessageBox.Show(String.Format("{0}", rd[0]));
            }
            conn.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        finally
        {
            conn.Close();
        }
    }
}

Please ignore all of the generic variables, I'm new to programming and am trying to do this all as a test run before I actually make a usable program.

stuartd · Accepted Answer · 2024-10-23 02:07:24Z

5

Remove the single quotes around the parameter in the sql string:

string cmdText = "Select [Tax EIN] From [TblClientInfo] Where [Client Name] = @client;";

While I'm here, I'm not a fan of .AddWithValue(), and there are a number of other improvements you can make as well:

selClient = comboBox1.SelectedItem.ToString();
string cmdText = "Select [Tax EIN] From [TblClientInfo] Where [Client Name] = @client;";

//whenever I see a "cmd2", I wonder about "cmd1"... 
//  that you probably can and should get this into a single call into the database
using (var conn = new SqlConnection("connection info"))
using (var cmd2 = new SqlCommand(cmdText, conn))
{
    //guessing a parameter type/length here. Use exact type from your DB.
    cmd2.Parameters.Add("@client", SqlDbType.NVarChar,50).Value = selClient;
    conn.Open();

    // I prefer my try/catch block to happen up at least one level
    // Code at that level is usually better positioned to react to the exceptions

    var rd = cmd2.ExecuteReader();
    while (rd.Read())
    {
        MessageBox.Show(rd[0].ToString());
    }
    //The main point of a using block with SqlConnection is that is safely closes the connection for you
}

edited Oct 23, 2024 at 2:07

stuartd

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answered May 30, 2016 at 22:29

Joel Coehoorn

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1 Comment

Abdellah OUMGHAR Over a year ago

Remove quotes from the second example.

Abdellah OUMGHAR · Accepted Answer · 2016-05-30 22:46:56Z

1

You must remove quotes '' from parameter @client :

string cmdText = "Select [Tax EIN] From [TblClientInfo] Where [Client Name] = @client;";

edited May 30, 2016 at 22:46

answered May 30, 2016 at 22:30

Abdellah OUMGHAR

3,7751 gold badge13 silver badges18 bronze badges

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