如何通过asp.net更新SQL Server数据库中的记录？

Question

我在asp.net中编写此代码，但仍未更新SQL Server数据库中的记录：

SqlCommand cmd4 = new SqlCommand("Select * from roomdetail", conn);
SqlDataReader dr = cmd4.ExecuteReader();

while (dr.Read())
    SqlCommand cmd3 = new SqlCommand("update [roomdetail] set [rid]=' " +count+1 + " '  where rid = 0 AND roomtype='"+typeRadioButtonList1.SelectedItem.ToString()+        "' ", conn);

Answer 1

正确使用ado.net的方法：

var newId = count + 1;
var roomType = typeRadioButtonList1.SelectedItem.ToString();

using (var connection = new SqlConnection("your db connection string here"))
{
        var query = "UPDATE [roomdetail] SET [rid] = @rid WHERE [rid] = 0 AND roomtype = @roomType";

        SqlCommand command = new SqlCommand(query, connection);
        command.Parameters.AddWithValue("@rid", newId);
        command.Parameters.AddWithValue("@roomType", roomType);

        try
        {
            command.Connection.Open();
            command.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            //handle exception
        }
}

Answer 2

您缺少ExecuteNonQuery方法，编写以下代码

SqlCommand cmd4 = new SqlCommand("Select * from roomdetail", conn);
SqlDataReader dr = cmd4.ExecuteReader();

while (dr.Read())
SqlCommand cmd3 = new SqlCommand("update [roomdetail] set [rid]=' " +count+1 + " '  where rid = 0 AND roomtype='"+typeRadioButtonList1.SelectedItem.ToString()+        "' ", conn);
cmd3.executeNonQuery();

Answer 3

假设连接已经打开，则在while循环中您将丢失以下语句：

cmd3.ExecuteNonQuery();

您必须执行命令才能更新数据库。