Question

我很难从SQL数据库中删除一行，我没有收到任何错误，它似乎工作正常，但没有删除任何内容。当我运行代码时，它将输出“NAME已被删除”

感谢您的帮助。

SqlConnection conn = new SqlConnection();
conn.ConnectionString = "Data Source=(LocalDB)\\v11.0;AttachDbFilename=|DataDirectory|\\MyDB.mdf;Integrated Security=True";

try
{
    conn.Open();
    SqlCommand Command = conn.CreateCommand();
    Command.CommandText = "DELETE FROM Contacts WHERE [First Name] = '@Name';";
    Command.Parameters.AddWithValue("@Name", DropDownList1.SelectedValue);
    Command.ExecuteNonQuery();
    TextBox1.Text = DropDownList1.SelectedValue + " Has Been Deleted";
}
catch (Exception ex)
{
    TextBox1.Text = "Nope";
}
finally
{
    conn.Close();
}

Answer 1

删除参数周围的引号。同时从参数中删除@ -sign，将其添加到命令中。

Command.CommandText = "DELETE FROM Contacts WHERE [First Name] = @Name;";
Command.Parameters.AddWithValue("Name", DropDownList1.SelectedValue);

Answer 2

您不需要带参数化查询的单引号。

Answer 3

您的标准很可能无法满足。（引用参数）所以没有记录被删除。

Command.ExecuteNonQuery();

返回记录计数的int。因此，您可以将此检查为零，以确保它已被删除。

Answer 4

以下详述的一些事项：

SqlConnection conn = new SqlConnection();
conn.ConnectionString = "Data Source=(LocalDB)\\v11.0;AttachDbFilename=|DataDirectory|\\MyDB.mdf;Integrated Security=True";

try
{
   conn.Open();
   SqlCommand Command = conn.CreateCommand();
   Command.CommandText = "DELETE FROM Contacts WHERE [First Name] = Name;"; // You don't need the '' or the '@' in your parameter name.
   Command.Parameters.AddWithValue("@Name", comboBox1.SelectedValue);
   if (Command.ExecuteNonQuery() > 0)  //  Add a conditional here that checks for > 0 and THEN set your validation text.
      textBox1.Text = comboBox1.SelectedValue + " Has Been Deleted";
}

catch (Exception ex)
{
   textBox1.Text = "Nope";
}

finally
{
   conn.Close();
}

从表中删除行似乎失败了

4 个答案: