必填参数未赋值，有值

Question

我正在使用 c#/ASP.NET 开发 Web 应用程序。作为应用程序的一部分，我想连接到 ms-access 数据库，并将其中的值放入 dataset.

出于某种原因，我在用 DataAdaptor 填充 dataset 时出现标题错误 - 尽管如此，当我使用断点时，我可以看到命令如下： SELECT ..... WHERE ItemID = @value0（如果您需要参数，请提出要求，我会复制整个内容）。

我还可以看到 @value0 的值 2 带有断点，我确信它是查询中的唯一值。

我的问题是，这怎么会发生？如果查询中的唯一值被填充，我错过了什么？

编辑：完整查询： SELECT ItemName as Name,ItemPicture as Picture,ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems FROM Item WHERE ItemID = @value0"

完整的建筑代码（为每个用户生成查询需要不同数量的项目，这个只有一个项目，所以我用它来测试）：

static public DataSet getUserShopItemDS(string username,List<shopItem> items)
{
string madeForCommand = "SELECT ItemName as Name,ItemPicture as Picture,ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems FROM Item WHERE ItemID = ";
        int count = 0;
        foreach (shopItem item in items)
        {
            madeForCommand += "@value"+count+" OR ";
            count++;
        }
        madeForCommand = madeForCommand.Substring(0, madeForCommand.Length - 3);
        OleDbCommand command = GenerateConnection(madeForCommand);
        for (int ii = 0; ii < items.Count; ii++)
        {
            command.Parameters.AddWithValue("@value" + ii, items[ii].ID);
        }
        var FreestyleAdaptor = new OleDbDataAdapter();
        FreestyleAdaptor.SelectCommand = command;
        DataSet Items = new DataSet();
        FreestyleAdaptor.Fill(Items);//The error is thrown here.
        return Items;
    }

编辑 2： - 商店商品 class：

public class shopItem
{
    //Irrelevant parameters,
    public int ID // Whenever a user logs in, I create a list of his items, and attach each one it's ID from the database. I send the list as a parameter to the function.
    {
        get;
        private set;
    }
    public shopItem(int ID)
    {
        this.ID = ID;
    }
    public shopItem() { }
    // more constructors.
}

Answer 1

这是您应该使用的代码：

        var madeForCommand = "SELECT ItemName as Name,ItemPicture as Picture,ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems FROM Item WHERE ";

        OleDbCommand command = new OleDbCommand();

        for (int ii = 0; ii < items.Count; ii++)
        {
            madeForCommand += "ItemId = ?  OR ";
            command.Parameters.AddWithValue("value" + ii, items[ii].ID);
        }

        madeForCommand = madeForCommand.Substring(0, madeForCommand.Length - 3);

在 MS Access 中，参数是使用 ?并且必须按照查询中使用的相同顺序提供。

必填参数未赋值，有值

No value given for required parameters, with value

c#

ms-access

oledb