"空值不能分配给类型System.Int32一个成员是一个非空的值类型" [英] "The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type."

问题描述

我有一个WCF服务（服务）。这些服务管理数据。但现在我有一个LINQ查询选择数据的问题。我得到一个消息的空值不能分配给类型System.Int32一个成员是一个非空的值类型。

I have a WCF service (services). The services manage the data. But now I have problems by selecting data in a LINQ-query. I get a message "The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type."

通过调试，我第一次通过方法走，你会完成对异常行。当我把后面的调试线（黄标）放入行// 08，然后我通过一切顺利的方法走。

By debugging the first time I walk through the method you'll finish to the exception-line. When I put back the debugger line (the yellow marked one) onto line "// 08", and then I walk through the method everything goes fine.

    private static ResultClass Geselecteerd(int AID_Artiest)  // 01
    { // 02
        ResultClass _Result = new ResultClass(); // 03
        string sMethodName = System.Reflection.MethodBase.GetCurrentMethod().Name;// 04
        // 05
        try // 06
        { // 07
            var recArtiest = (from artiest in DatabaseControl.GetDatabeheer.DataContext.ARTIESTs  // 08
                           where artiest.ID_ARTIEST == AID_Artiest
                           select artiest).SingleOrDefault();

            if (recArtiest != null)
            {
                ArtiestDataType.ID_Artiest = recArtiest.ID_ARTIEST;
                ArtiestDataType.Artiestnaam = recArtiest.ARTIESTNAAM;
                ArtiestDataType.Voorvoegsel = recArtiest.VOORVOEGSEL;
                ArtiestDataType.Product = recArtiest.PRODUCT;
                ArtiestDataType.ID_Categorie = recArtiest.ID_CATEGORIE;
                ArtiestDataType.ID_Genre = recArtiest.ID_GENRE;
                ArtiestDataType.Is_Band = BasisDataType.GetBoolString(recArtiest.IS_BAND);
                ArtiestDataType.Land = recArtiest.LAND;
                ArtiestDataType.Plaats = recArtiest.PLAATS;
                ArtiestDataType.Website = recArtiest.WEBSITE;
                ArtiestDataType.DatumInvoer = recArtiest.DATUM_INVOER;
                ArtiestDataType.DatumMutatie = recArtiest.DATUM_MUTATIE;
            }
        }
        catch (Exception ex)
        {
            string sFoutmelding = "Kan geen selectie maken.";
            FLogboek.AddFoutmelding(FClassName, sMethodName, sFoutmelding, ex.Message);

            _Result.Code = ResultCode.FATAAL;
            _Result.Melding = sFoutmelding;
        }

        return _Result;
    }

ID_ARTIEST是一个整数字段，它是主键了。需要字段的值和NULL值是不可能的。

这个方法一直工作。当我添加新的服务问题开始

我的问题是：什么我错了？具有与服务呢？ 我必须拖延这一进程？
能有人给我一些建议吗？我已经8服务引用。如果你缺少一些必要的资源，我可以添加它。

My question is: What do I wrong? Has is to do with the service? Do I have to delay the process? Can anybody give me some tips? I've 8 service references. If you're missing some essential sources, I can add it.

我现在只有一个变通。
我已经加入的try-catch在try-catch区域内。然后，我没有得到任何的异常。它具有与性能有关。 我需要一个异步的解决方案？

I have now only a work-around. I have added try-catch inside the try-catch area. And then I didn't get any exception. It has to do with the performance. Do I need an Async-solution?

感谢。

推荐答案

几乎可以肯定发生了什么是类型 ARTIESTs 在 DatabaseControl.GetDatabeheer.DataContext.ARTIESTs 的类型 INT？（这意味着空整型）的。

Almost certainly what is happening is one of the properties of the type ARTIESTs in DatabaseControl.GetDatabeheer.DataContext.ARTIESTs is of type int? (which means nullable integer).

在猜测我会说这是不是 ID_CATEGORIE 或 ID_GENRE 。

At a guess I would say it's either ID_CATEGORIE or ID_GENRE.

您将需要修改你的类型的等值财产 ArtiestDataType 也属于类型<$的C $ C> INT？。

You will need to modify the equivalent property of your type ArtiestDataType to also be of type int?.

这将解决您的问题。

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