window form database connection(INSERT)

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C#

SQL

WinForms

connectionstring

Hi guys
i am inserting a string and a int into a database. There is no error but the code below didn't work. i am thinking it is the connectionstring which work on my WPF application. Can you please advise me on what went wrong. TIA! :D

string a = textBox1.Text;
            string b = comboBox1.Text;
            string c = a + b;
            int l = 0;
            if (textBox1.Text == "")
            {
                MessageBox.Show("Please Enter a Video's Name!", "Information",
                   MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else if (comboBox1.Text == "")
            {
                MessageBox.Show("Please select Video's extension", "Information",
                   MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {

                SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Video.MDF;Integrated Security=True;User Instance =True");
                SqlCommand comm = new SqlCommand("INSERT INTO Video VALUES('" + a + b + "'," + l + ")", con);
                SqlDataAdapter da = new SqlDataAdapter(comm);
                con.Open();
                comm.ExecuteNonQuery();
}