C# window application

The issue comes due to the parameter called @pcode is not passed or used in your query. For that u can check in your c# code or your sql server query if any stored procedure or any functions u have used.

Check the other parameters where these are used the same way u can put the @pcode paramter there in ur c# code or sql server query.

Problem

The error message mentioned in the problem description is not provided. However, based on the code, there are a few potential issues that could cause errors:

1. Null Reference Exception: If the txtQty textbox is empty or contains invalid data, parsing it to an integer (_qty = int.Parse(txtQty.Text)) could throw a FormatException or a NullReferenceException.

2. SQL Injection Vulnerability: The code concatenates the txtPSearch.Text directly into the SQL query string, which can lead to SQL injection attacks. It is recommended to use parameterized queries to prevent this vulnerability.

Cause

Without the specific error message, it is difficult to determine the exact cause of the error. However, based on the code analysis, the potential causes could be:

1. Invalid or empty value in the txtQty textbox, leading to a parsing error.

2. Invalid barcode value in the txtPSearch textbox, causing the SQL query to return no rows.

3. Database connection issues, such as incorrect connection string or database server unavailability.

Solution

To address the potential issues mentioned above, follow these steps:

1. Validate the txtQty textbox value before parsing it to an integer. You can use the int.TryParse method to safely convert the value without throwing an exception. Here's an example:

2. if (int.TryParse(txtQty.Text, out _qty))
   {
       // The parsing was successful, continue with the code
       // ...
   }
   else
   {
       // The value in txtQty is invalid, show an error message or handle it accordingly
       MessageBox.Show("Invalid quantity value.", stitle, MessageBoxButtons.OK, MessageBoxIcon.Warning);
   }
   

3. Implement parameterized queries to prevent SQL injection attacks. Here's an example of how to modify the SQL query using parameters:

4. cm = new SqlCommand("SELECT * FROM tblProduct WHERE barcode LIKE @barcode", cn);
   cm.Parameters.AddWithValue("@barcode", txtPSearch.Text);
   

5. Ensure that the database connection is properly established and closed. In the provided code, the connection is closed in the catch block, but it should also be closed in the success scenario. Consider using the using statement to automatically dispose of the connection object:

6. using (SqlConnection cn = new SqlConnection(connectionString))
   {
       // Code that uses the connection
   }
   

    

Ohk, I will check and revert please 

Please check if the required parameter is supplied to query, I dont see the required parameter is passed. 

Please this is my parameter before is not working, kindly check it and help. thank you in advance 

private void AddToCart(String _pcode, double _price, int _qty)
        {
            String id = "";
            bool found = false;
            int cart_qty=0;
            cn.Open();
            cm = new SqlCommand("select * from tblCart where transno=@transno and pcode=@pcode", cn);
            cm.Parameters.AddWithValue("@transno", lblTransno.Text);
            cm.Parameters.AddWithValue("@pcode", _pcode);
            dr = cm.ExecuteReader();
            dr.Read();
            if (dr.HasRows)
            {
                found = true;
                id = dr["id"].ToString();
                cart_qty = int.Parse(dr["qty"].ToString());
            }
            else
            {
                found = false;
            }
            dr.Close();
            cn.Close();

             if(found == true)
               {
                   // validate product quantity by adding and subtracting
                   if (qty < int.Parse(txtQty.Text)+ cart_qty)
                   {
                       MessageBox.Show("Unable to proceeed. Remaining qty on hand is " + qty, "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                       return;
                   }

                   cn.Open();
                   cm = new SqlCommand("update tblCart set qty = (qty +" +_qty+") where id='"+id+"'", cn);
                   cm.ExecuteNonQuery();
                   cn.Close();

                   txtPSearch.SelectionStart = 0;
                   txtPSearch.SelectionLength = txtPSearch.Text.Length;
                  LoadCart();
                this.Dispose();
               }else
               {

                   // validate product quantity to show avoid selling when product is out of stock 
                   if (qty < int.Parse(txtQty.Text))
                   {
                       MessageBox.Show("Unable to proceeed. Remaining qty on hand is " + qty, "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                       return;
                   }

                   cn.Open();
                   cm = new SqlCommand("insert into tblCart (transno, pcode, price, qty, sdate, cashier)values(@transno, @pcode, @price, @qty, @sdate,@cashier)", cn);
                   cm.Parameters.AddWithValue("@transno", lblTransno.Text);
                   cm.Parameters.AddWithValue("@pcode", _pcode);
                   cm.Parameters.AddWithValue("@price", _price);
                   cm.Parameters.AddWithValue("@qty", _qty);
                   cm.Parameters.AddWithValue("@sdate", DateTime.Now.ToString("dd-MM-yyyy"));
                   cm.Parameters.AddWithValue("@cashier", lblUser.Text);
                   cm.ExecuteNonQuery();
                   cn.Close();
                   MessageBox.Show("Product quatity has been successfully added", stitle, MessageBoxButtons.OK, MessageBoxIcon.Information);
                   txtPSearch.SelectionStart = 0;
                   txtPSearch.SelectionLength = txtPSearch.Text.Length;
                   LoadCart();
                  this.Dispose();
               }
            }
        

required paramater is not supplied to query.