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I have placed this code under the insert button that transfers the values from the textboxes to the datagridview.

for (int nCounter = 0; nCounter <= dataGridView1.RowCount - 1; nCounter++)
                if (txtrawmatno.Text == dataGridView1[2, nCounter].Value.ToString())
                    MessageBox.Show("That product has been selected already.", "Repeat", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);


I'm getting an error that says: Object reference not set to an instance of an object.
please help! I want to validate the text box value to avoid entering a duplicate.

1 solution

Object reference not set to an instance of an object

This error happens when you try to use a property or call a method of an object that is null. More details: here[^]

A simple use of Visual studio DEBUGGER can tell you the object because of which it is happening. Just look at the stack trace and put a debugger on that line. Check the objects of that line and see if any one is null and you are trying to use that objects property. Handle the same.
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