Question

Try, Catch

Asked by: metta0_3

I have this simple connection to database. I need a try, catch in case of a failed connection. Can anyone assist in placing it in. I cannot get it to work.

protected void GetVendorsInfo_SelectedIndexChanged(object sender, EventArgs e)
    {
        string myString = drpInputVendor.SelectedValue;
        ClearControls();

       
        if (myString != "Select A Vendor")
        {
            SqlConnection conn = new SqlConnection(connectionString);
            conn.Open();
            SqlCommand cmd = new SqlCommand("SelectedVendor", conn);

            SqlParameter inputParam1 = new SqlParameter("@myVendCode", SqlDbType.VarChar, 15);
            inputParam1.Value = drpInputVendor.SelectedValue;
           
            SqlParameter inputParam2 = new SqlParameter("@myItemNo", SqlDbType.VarChar, 15);
            inputParam2.Value = txtInputItemCode.Text;

            SqlParameter outputParam = new SqlParameter("@result", SqlDbType.VarChar, 15);
            outputParam.Direction = ParameterDirection.Output;
            cmd.CommandType = CommandType.StoredProcedure;

            cmd.Parameters.Add(inputParam1);
            cmd.Parameters.Add(inputParam2);
            cmd.Parameters.Add(outputParam);

            SqlDataAdapter dataAdapter = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            dataAdapter.Fill(ds);

            DataTable dt = ds.Tables[0];            

            foreach (DataRow dr in dt.Rows)
            {
                txtInputVendorPartNo.Text = dr.ItemArray[0].ToString();

                txtInputBoxQty.Text = dr.ItemArray[1].ToString();
                txtInputBoxQty.Text = txtInputBoxQty.Text.Split('.')[0];
            }

            conn.Close();
        }
        RetrieveRemainder();
    }

Regards...

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Asked On
2009-10-27 at 00:07:37ID24846315
Topics

C# Programming Language

,

Programming for ASP.NET

,

MS SQL Server

Participating Experts
3
Points
500
Comments
5

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Answers

 

by: dhansmaniPosted on 2009-10-27 at 00:27:07ID: 25669792

here i added code

protected void GetVendorsInfo_SelectedIndexChanged(object sender, EventArgs e)
		{
			string myString = drpInputVendor.SelectedValue;
			ClearControls();
                         SqlConnection conn = new SqlConnection(connectionString);
                     SqlCommand cmd; 
 
			if (myString != "Select A Vendor")
			{
				try
				{
					
					conn.Open();
					cmd =  new SqlCommand("SelectedVendor", conn);
 
 
					SqlParameter inputParam1 = new SqlParameter("@myVendCode", SqlDbType.VarChar, 15);
					inputParam1.Value = drpInputVendor.SelectedValue;
 
					SqlParameter inputParam2 = new SqlParameter("@myItemNo", SqlDbType.VarChar, 15);
					inputParam2.Value = txtInputItemCode.Text;
 
					SqlParameter outputParam = new SqlParameter("@result", SqlDbType.VarChar, 15);
					outputParam.Direction = ParameterDirection.Output;
					cmd.CommandType = CommandType.StoredProcedure;
 
					cmd.Parameters.Add(inputParam1);
					cmd.Parameters.Add(inputParam2);
					cmd.Parameters.Add(outputParam);
 
					SqlDataAdapter dataAdapter = new SqlDataAdapter(cmd);
					DataSet ds = new DataSet();
					dataAdapter.Fill(ds);
 
					DataTable dt = ds.Tables[0];
 
					foreach (DataRow dr in dt.Rows)
					{
						txtInputVendorPartNo.Text = dr.ItemArray[0].ToString();
 
						txtInputBoxQty.Text = dr.ItemArray[1].ToString();
						txtInputBoxQty.Text = txtInputBoxQty.Text.Split('.')[0];
					}
				}
 
				catch (SqlException exSQL)
				{
					Debug.WriteLine(exSQL.Message);
 
					if (conn.State != ConnectionState.Closed)
					{
						conn.Close();
					}
					cmd.Dispose();
					conn.Dispose();
				}
				catch (Exception ex)
				{
					Debug.WriteLine(ex.Message);
 
					if (conn.State != ConnectionState.Closed)
					{
						conn.Close();
					}
					cmd.Dispose();
					conn.Dispose();
				}
				finally
				{
					if (conn.State != ConnectionState.Closed)
					{
						conn.Close();
					}
					cmd.Dispose();
					conn.Dispose();
 
					//reader = null;
 
				} 
 
				conn.Close();
			}
			RetrieveRemainder();
		}
                                              
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by: x_comPosted on 2009-10-27 at 00:27:36ID: 25669795

Hi metta0_3,
>>...I need a try, catch in case of a failed connection.
Just put inside try/catch block in the preferable block that may return any error in the end.
eg:

protected void GetVendorsInfo_SelectedIndexChanged(object sender, EventArgs e)
    {
        try{
          //....your existing applied code...
        }catch(Exception  e){
          Response.write("error returned: " + e.ToString())
        }
     }

Check this MSDN site for better understanding of try/catch block practices:
http://msdn.microsoft.com/en-us/library/0yd65esw.aspx

 

by: dhansmaniPosted on 2009-10-27 at 00:29:15ID: 25669802

here i forgot remove ' conn.Close();' before Retrieveremainder(). Remove it( conn.Close();
                       

 

by: arturrrroPosted on 2009-10-27 at 00:52:28ID: 25669928

Also look at the "using" c# keyword. It makes the code a lot more clear.

using (SqlConnection cn = new SqlConnection(connectionString))
{
        cn.Open();
        // rest of the code
}

is equivalent to:

SqlConnection cn =  null;
try
{
    cn = new SqlConnection(connectionString);
    cn.Open();
    // rest of the code
}
finally
{
    if (null != cm);
        cm.Dispose();
}

Note that Dispose() method of the SqlConnection actually checks if the connection is open , and calls Close() if it is so.

Below is the skeleton of the code I would prefer in my app.

                try
                {
                    using (SqlConnection conn = new SqlConnection("connstr"))
                    {
 
                        conn.Open();
                        using (SqlCommand cmd = new SqlCommand("SelectedVendor", conn))
                        {
                            // you code here
                        }
                    }
                }
                catch (SomeException)
                {
                    // Handle exception 1 here
                }
                catch (SqlException e)
                {
                    //Handle exception 2 here
                }
                catch (Exception e)
                {
                    // Handle other exceptions here
                }

                                              
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by: metta0_3Posted on 2009-10-27 at 01:04:16ID: 31646316

You sir are a star!

20120131-EE-VQP-002

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