Question

首先，请帮帮我！我再也无法忍受了。我找不到错误的位置。这是我的问题：

我正在尝试通过c＃winform应用程序更新一行。从应用程序生成的更新查询格式正确。我在sql server环境中测试过它，效果很好。当我从应用程序运行它时，我得到0行更新。

以下是使用反射生成更新语句的代码段 - 请勿尝试弄清楚。在代码部分后继续阅读：

        public void Update(int cusID)
        {
            SqlCommand objSqlCommand = new SqlCommand();
            Customer cust = new Customer();

            string SQL = null;

            try
            {
                if ((cusID != 0))
                {
                        foreach (PropertyInfo PropertyItem in this.GetType().GetProperties())
                        {
                            if (!(PropertyItem.Name.ToString() == cust.PKName))
                            {
                                if (PropertyItem.Name.ToString() != "TableName")
                                {
                                    if (SQL == null)
                                    {
                                        SQL = PropertyItem.Name.ToString() + " = @" + PropertyItem.Name.ToString();
                                    }
                                    else
                                    {
                                        SQL = SQL + ", " + PropertyItem.Name.ToString() + " = @" + PropertyItem.Name.ToString();
                                    }
                                 }
                                 else
                                 {
                                    break;
                                 }
                            }
                       }

                        objSqlCommand.CommandText = "UPDATE " + this.TableName + " SET " + SQL + " WHERE " + cust.PKName + " = @cusID AND PhoneNumber = " + "'" + "@phNum" + "'";

                        foreach (PropertyInfo PropertyItem in this.GetType().GetProperties())
                        {
                            if (!(PropertyItem.Name.ToString() == cust.PKName))
                            {
                                if (PropertyItem.Name.ToString() != "TableName")
                                {
                                    objSqlCommand.Parameters.AddWithValue("@" + PropertyItem.Name.ToString(), PropertyItem.GetValue(this, null));
                                }
                                else
                                {
                                    break;
                                }

                            }
                        }

                        objSqlCommand.Parameters.AddWithValue("@cusID", cusID);
                        objSqlCommand.Parameters.AddWithValue("@phNum", this.PhoneNumber);
                        DAL.ExecuteSQL(objSqlCommand);
                }
                else
                {
                    //AppEventLog.AddWarning("Primary Key is not provided for Update.")
                }

            }
            catch (Exception ex)
            {
                //AppEventLog.AddError(ex.Message.ToString)
            }
        }

以下部分：

objSqlCommand.CommandText = "UPDATE " + this.TableName + " SET " + SQL + " WHERE " + cust.PKName + " = @cusID AND PhoneNumber = " + "'" + "@phNum" + "'";

生成dml：

UPDATE CustomerPhone SET PhoneTypeID = @PhoneTypeID, PhoneNumber = @PhoneNumber WHERE CustomerID = @cusID AND PhoneNumber = '@phNum'

@PhoneTypeID和@PhoneNumber来自两个属性。我们从用户输入文本框中为表示层中的这些属性赋值。获取值的下面部分：

objSqlCommand.Parameters.AddWithValue("@" + PropertyItem.Name.ToString(), PropertyItem.GetValue(this, null));

以下代码填写WHERE：

的值

                    objSqlCommand.Parameters.AddWithValue("@cusID", cusID);
                    objSqlCommand.Parameters.AddWithValue("@phNum", this.PhoneNumber);

最终代码应如下所示：

UPDATE CustomerPhone 
SET PhoneTypeID = 7, PhoneNumber = 999444
WHERE CustomerID = 500 AND PhoneNumber = '911';

电话类型ID为7 - 从文本框中获取的用户值电话号码是999444 - 从文本框中获取的用户值

上面的最终更新语句适用于sql环境，但在运行时通过应用程序，执行非查询运行正常并更新0行！我想知道为什么？

Answer 1

这是问题所在：

AND PhoneNumber = '@phNum'

正在查找的电话号码正好是文字'@phNum' - 使用名为phNum的参数。你想要

AND PhoneNumber = @phNum

你也没有明显的原因打破你的字符串文字。这句话：

objSqlCommand.CommandText = "UPDATE " + this.TableName + " SET " + SQL + 
    " WHERE " + cust.PKName + " = @cusID AND PhoneNumber = " + 
    "'" + "@phNum" + "'";

将更容易阅读：

objSqlCommand.CommandText = "UPDATE " + this.TableName + " SET " + SQL +
    " WHERE " cust.PKName + " = @cusID AND PhoneNumber = '@phNum'";

显然你想从它中删除单引号，只需：

objSqlCommand.CommandText = "UPDATE " + this.TableName + " SET " + SQL +
    " WHERE " cust.PKName + " = @cusID AND PhoneNumber = @phNum";

一点点重构也不会有问题。这个循环：

foreach (PropertyInfo PropertyItem in this.GetType().GetProperties())
{
    if (!(PropertyItem.Name.ToString() == cust.PKName))
    {
        if (PropertyItem.Name.ToString() != "TableName")
        {
            if (SQL == null)
            {
                SQL = PropertyItem.Name.ToString() + " = @" + PropertyItem.Name.ToString();
            }
            else
            {
                SQL = SQL + ", " + PropertyItem.Name.ToString() + " = @" + PropertyItem.Name.ToString();
            }
         }
         else
         {
            break;
         }
    }

}

会更简单，更具可读性：

StringBuilder sqlBuilder = new StringBuilder();
foreach (PropertyInfo property in this.GetType().GetProperties())
{
    string name = property.Name;
    // I believe you had a bug before - the properties being updated
    // would depend on the ordering of the properties - if it
    // ran into "TableName" first, it would exit early!
    // I *suspect* this is what you want
    if (name != cust.PKName && name != "TableName")
    {
        sqlBuilder.AppendFormat("{0} = @{0}, ", name);
    }
}
// Remove the trailing ", "
if (sqlBuilder.Length > 0)
{
    sqlBuilder.Length -= 2;
}

您也可以使用最终循环执行类似的操作。

Answer 2

PhoneNumber是字符串还是整数？

我认为你是SET整数，但是以WHERE作为文字检查。这不是问题吗？

如果是整数，请尝试：

UPDATE CustomerPhone 
SET PhoneTypeID = 7, PhoneNumber = 999444
WHERE CustomerID = 500 AND PhoneNumber = 911;

如果是字符串，请尝试：

UPDATE CustomerPhone 
SET PhoneTypeID = 7, PhoneNumber = '999444'
WHERE CustomerID = 500 AND PhoneNumber = '911';

通过C＃Winform应用程序更新语句更新0行？

2 个答案: