private void BtnLogin_Click(object sender, EventArgs e) { CalculatorServiceClient client = new CalculatorServiceClient("Username"); try { client.ClientCredentials.UserName.UserName = txtUsername.Text; client.ClientCredentials.UserName.Password = txtPassword.Text; client.Open(); client.Login(); Form form = new Calculator(txtUsername.Text, txtPassword.Text); this.Hide(); form.Show(); client.Close(); } catch (Exception exception) { MessageBox.Show(exception.InnerException.Message); client.Abort(); } }