How Do I Multiply A List Column With A Texbox Text?

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Please help me check where i comment

C#

private void addbtn_Click(object sender, EventArgs e)
       {
           string connectionstring = @"Data Source=.;Initial Catalog=SuperM;Integrated Security=True";
           SqlConnection sqlcon = new SqlConnection(connectionstring);
           sqlcon.Open();

           SqlCommand cm = new SqlCommand("Select ID, Item_Code, quantity, price from stock where item_code = '" + itemcodetxt.Text + "'", sqlcon);

           SqlDataReader reader = cm.ExecuteReader();

           listView1.View = View.Details;
 while (reader.Read())
           {
               var item = new ListViewItem();
               item.Text = reader["ID"].ToString();
               item.SubItems.Add(reader["item_code"].ToString());
               item.SubItems.Add(quantitytxt.Text);
               item.SubItems.Add(reader["price"].ToString());

             //please check here
 item.SubItems.Add(listView1.Items[3].ToString() * listView1.Items[2].ToString());
               listView1.Items.Add(item);


           }

Posted 18-Nov-15 2:58am

Member 11673987

Updated 18-Nov-15 3:09am

phil.o

v2

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glen205 18-Nov-15 9:11am

What error is the code throwing?

It looks like you're trying to multiply two strings together, this won't end well....

Cast (parse or TryParse) the items to a numeric datatype e.g. int otherwise you won't be able to perform multiplication...

3 solutions

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phil.o · Answer 1 · 2015-11-18T03:14:00

Solution 1

What do you expect by multiplicating strings? What if these strings are not valid number representations.

All arithmetic methods must be run against numbers, not strings.

Tip:

C#

decimal quantity, price, total;
if (decimal.TryParse(listView1.Items[3].ToString(), out price) && decimal.TryParse(listView1.Items[2].ToString(), out quantity)) {
   total = price * quantity;
}
else {
   // There is a problem with either the price, or the quantity, which is not a valid number representation
}

Posted 18-Nov-15 3:14am

phil.o

Comments

Member 11673987 18-Nov-15 9:45am

InvalidArgument=Value of '3' is not valid for 'index'.
Parameter name: index

that was the error message i received

phil.o 18-Nov-15 10:07am

Then you have to debug your code and see where it fails.
Obviously the index is out of the array's bounds; that's a perfect job for a debugging session.

Abhinav S · Answer 2 · 2015-11-18T03:14:00

Solution 2

Try item.SubItems.Add(Convert.ToInt(listView1.Items[3]) * Convert.ToInt(listView1.Items[2]));
A neater way would be to use Int32.TryParse[^] to make sure that the values inside the list view columns are integers,

Posted 18-Nov-15 3:14am

Abhinav S

Comments

Member 11673987 18-Nov-15 9:29am

The price is coming from database

BillWoodruff 18-Nov-15 10:42am

try Sri Abhninav's suggestion and see if it works !

Abhinav S 18-Nov-15 11:12am

Shukriya BillWoodJi.

Matt T Heffron · Answer 3 · 2015-11-18T07:53:00

A couple of things:
1. Switch to using a parameterized query for the SQL to avoid the risk of SQL injection issues:

C#

private void addbtn_Click(object sender, EventArgs e)
{
  string connectionstring = @"Data Source=.;Initial Catalog=SuperM;Integrated Security=True";
  SqlConnection sqlcon = new SqlConnection(connectionstring);
  sqlcon.Open();
 
  SqlCommand cm = new SqlCommand("Select ID, Item_Code, quantity, price from stock where item_code = @ICode", sqlcon);

  SqlParameter param = cm.Parameters.Add("@ICode", SqlDbType.NVarChar);
  param.Value = itemcodetxt.Text; 
  SqlDataReader reader = cm.ExecuteReader();

2. As others have said, you cannot multiply strings. This also brings the question of what are the data types in the DB? I'm going to assume that the price column has a numeric data type like Integer, Single, Double, Currency.

C#

int quantity; // I'm assuming this is actually an integer
if (!int.TryParse(quantitytxt.Text, out quantity))
{
  // the input is invalid, you decide how you want to handle this case!
}
while (reader.Read())
{
  var item = new ListViewItem();
  item.Text = reader["ID"].ToString();
  item.SubItems.Add(reader["item_code"].ToString());
  item.SubItems.Add(quantitytxt.Text);
  decimal price = Convert.ToDecimal(reader["price"]); // a cast might be sufficient
  item.SubItems.Add(price.ToString());

  item.SubItems.Add((quantity * price).ToString());
  listView1.Items.Add(item);
}

The above code has not been tried...

How Do I Multiply A List Column With A Texbox Text?

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