Logic Improvement on Code: Get the Supplier ID of selected Supplier Name (combobox value) to appear in a textbox

Question

1.00/5 (1 vote)

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This code works after selecting an item in the combo box --but when I change the selected item-- I get an error.

Can you help me fix this code?

C#

string query = "select SupplierNo from Supplier WHERE SupplierName = '" + cbosupplier.SelectedItem.ToString() + "'";
              SqlCommand cmd = new SqlCommand(query, cn);
              cmd.CommandText = query;

              
              SqlDataReader rdr = cmd.ExecuteReader();

              while (rdr.Read())
              {
                  
                  txtsupplierno.Text = rdr["SupplierNo"].ToString();
              }

Posted 27-Jun-12 14:35pm

wolfsor

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Comments

Sergey Alexandrovich Kryukov 27-Jun-12 20:58pm

How? You don't show your event handler on selection changed.
You string concatenation '+' with the query text is just unacceptable -- use parametrized query.
--SA

DamithSL 27-Jun-12 23:25pm

What is the error you get?

wolfsor 28-Jun-12 4:24am

"There is already an open DataReader associated with this Command which must be closed first." I added "rdr.close();" to close it

2 solutions

Solution 2

at the bottom, I added:

C#

rdr.close();

Posted 27-Jun-12 22:22pm

wolfsor

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DamithSL · Accepted Answer · 2012-06-27T17:14:00

you can check cbosupplier.SelectedItem value before search on database.

if there is empty or default value, you can avoid before search

C#

var supplier = cbosupplier.SelectedItem.ToString();
if(!string.IsNotNullOrEmpty(supplier)|| supplier != "please Select supplier")
{
  // search on Database
}

And you need to use Parameters[^]

and Also check for null before call ToString

C#

if (rdr["SupplierNo"] != DBNull.Value)
{
    ltlAdditional.Text = rdr["SupplierNo"].ToString();
}

One more thing:

If you need to Append Text use

C#

ltlAdditional.Text += rdr["SupplierNo"].ToString();