Data not inserting into database

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C#

SQL

The Problem I have is that my data is not being submitted into the database or the datatable at all when I click on the save button.

What supposed to happen is that the user (or me) for this instance is supposed to enter the information in two textboxes then click on the save button to enter the information in the database. However it doesn't save in the database or does show in the gridview even though it says and looks like the data is being saved.

There are no errors in my code. It's a simple sign in form that i'm creating so i'm not to worried about sql injection at this moment. although I will add code to prevent sql injection once i'm done with the project. I will continue to debug and look for solutions. If anyone can answer or address this issue it would be greatly appreciated.

My code is below and please note I did not copy and paste this code from the internet I wrote it myself. Again thank you for your time if anyone can help me.

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\ComputerLab.mdf;Integrated Security=True");
            SqlCommand cmd = new SqlCommand("sp_insert", con);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@LASTNAME", metroTextBox1.Text);
            cmd.Parameters.AddWithValue("@COMPUTER", metroTextBox2.Text);
            con.Open();
            int i = cmd.ExecuteNonQuery();

            con.Close();

            if (i != 0)
            {
                MessageBox.Show(i + "Data Saved");
            }

What I have tried:

I have debugged the program. Tested the connection string. nothing I have thought of so far has seemed to help the situation any.