Question

我想要删除数据库的记录。我想先检查这条记录是否存在，是否存在继续，但是如果不存在，则显示带有消息框的消息。我不知道如何设置此检查。任何想法？这是我的代码：

if (textBoxCode.Text != String.Empty && textBoxLastName.Text != String.Empty && textBoxFirstName.Text != String.Empty)

{
  con.Open();

  SqlCommand cmd = con.CreateCommand();
  cmd.CommandType = CommandType.Text;
  cmd.CommandText = "delete from Student where Code='" + textBoxCode.Text + "' and Last_Name='" + textBoxLastName.Text + "' and First_Name='" + textBoxFirstName.Text + "'";
  cmd.ExecuteNonQuery();

  con.Close();
  DisplayData();

  MessageBox.Show("Student deleted successfully", "Delete Done", MessageBoxButtons.OK);

  textBoxCode.Text = String.Empty;
  textBoxFirstName.Text = String.Empty;
  textBoxLastName.Text = String.Empty;

}

Answer 1

您可以使用ExecuteNonQuery函数的返回值。

if (textBoxCode.Text != String.Empty && textBoxLastName.Text != String.Empty && textBoxFirstName.Text != String.Empty)
{

    con.Open();

    SqlCommand cmd = con.CreateCommand();
    cmd.CommandType = CommandType.Text;
    cmd.CommandText = "delete from Student where Code=@Code and Last_Name=@Last_Name and First_Name=@First_Name";
    cmd.Parameters.AddWithValue("@Code", textBoxCode.Text);
    cmd.Parameters.AddWithValue("@Last_Name", textBoxLastName.Text);
    cmd.Parameters.AddWithValue("@First_Name", textBoxFirstName.Text);

    int rc = cmd.ExecuteNonQuery();

    if (rc > 0)
    {
        MessageBox.Show("Student deleted successfully", "Delete Done", MessageBoxButtons.OK);
    }
    else
    {
        MessageBox.Show("There is no record found for delete!", "Delete Done", MessageBoxButtons.OK);
    }
    con.Close();
    DisplayData();

    textBoxCode.Text = String.Empty;
    textBoxFirstName.Text = String.Empty;
    textBoxLastName.Text = String.Empty;

}

在删除之前尝试检查数据库中是否存在记录

1 个答案: