login failed for user error

private void button1_Click(object sender, EventArgs e)

{

try

{

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["WindowsFormsApplication1.Properties.Settings.Database1ConnectionString"].ConnectionString);

con.Open();

SqlCommand com = new SqlCommand("insert into tt values('" + textBox1.Text + "')", con);

int h = com.ExecuteNonQuery();

if (h > 0)

{

MessageBox.Show("saved");

}

con.Close();

}

catch(Exception ex)

{

MessageBox.Show(ex.Message);

}