无法将数组转换为通用列表

Question

您好，我在将数组转换为通用列表时遇到了问题。它引发了如下错误。在课堂上，我已经以 ToList 的身份返回，但为什么我仍然会出现。我已经将服务引用返回类型更改为通用列表，默认情况下是 Array，但它获取 System.Collection.GenericList 无法转换为 System.Collection.Genericlist。请帮忙谢谢

Public Function GetMerchantList() As List(Of Merchant) Implements IMerchant.GetMerchantList
    Dim ws As New aMerchantService.MerchantServiceClient

    Dim General As New General
    Dim kWSUrl As String = ""

    Dim endpointAddress = ws.Endpoint.Address

    Dim newEndpointAddress As New EndpointAddressBuilder(endpointAddress)
    kWSUrl = General.ConvertWsURL("App")

    newEndpointAddress.Uri = New Uri(kWSUrl & "MerchantService.svc")
    ws = New aMerchantService.MerchantServiceClient("BasicHttpBinding_IMerchantService", newEndpointAddress.ToEndpointAddress())
    Dim Data = ws.GetMerchantList()

    Return Data
End Function

商家类

  Public Function GetMerchantList() As List(Of Merchant)
        Dim Db As New TTMSEntities
        Dim Data = (From p In Db.TT_MERCHANT Join r In Db.TT_BRANCH_SETTING On _
                   p.MERCHANT_BRANCH_INTERNAL_NUM Equals r.INTERNAL_NUM _
                   Select New Merchant With {.MerchantID = p.MERCHANT_ID,
                                             .MerchantName = p.DESCRIPTION,
                                             .BranchID = r.INTERNAL_NUM,
                                             .BranchName = r.BRANCH_DESC})

        If Data IsNot Nothing Then
            Return Data.ToList
            '  Return ConvertMerchant(Data.ToList)
        Else
            Return Nothing
        End If
    End Function

错误

The error is Error Value of type '1-dimensional array of TTMS.App.WebSites.Data.Merchant' cannot be converted to 'System.Collections.Generic.List(Of TTMS.Web.WebSites.WCF.Merchant)'.

Answer 1

您需要可以将TTMS.App.WebSites.Data.Merchant 映射到TTMS.Web.WebSites.WCF.Merchant 的逻辑，即使它们是相同的，因为就 .NET 而言它们是两种不同的类型。

类似这样的：

Dim MapppedData As New List(Of Data.Merchant)
Dim Data = ws.GetMerchantList()

For Each theMerchant As WCF.Merchant In data
    ' Do logic here to map each of the fields in the 
    ' corresponding Merchant classes

    ' Add mapped Merchant (Data.Merchant) to the list

Next

' Return the mapped list of Data.Merchant objects
Return MappedData

---

更新：

我建议重命名 WCF 服务中的方法和类，以使它们与调用层中的不匹配，如下所示：

Public Class WsMerchant

End Class

Public Function GetMerchants() As List(Of WsMerchant)

End Function

现在，您的 WCF 服务层正在返回一个名称与尝试使用它的层不冲突的对象。因此，您的调用函数 (GetMerchantList()) 现在是这样的：

Public Function GetMerchantList() As List(Of Merchant) Implements IMerchant.GetMerchantList
    Dim ws As New aMerchantService.MerchantServiceClient

    Dim General As New General
    Dim kWSUrl As String = ""

    Dim endpointAddress = ws.Endpoint.Address

    Dim newEndpointAddress As New EndpointAddressBuilder(endpointAddress)
    kWSUrl = General.ConvertWsURL("App")

    newEndpointAddress.Uri = New Uri(kWSUrl & "MerchantService.svc")
    ws = New aMerchantService.MerchantServiceClient("BasicHttpBinding_IMerchantService", newEndpointAddress.ToEndpointAddress())

    Dim MapppedData As New List(Of Merchant)
    Dim Data = ws.GetMerchantList()

    For Each theMerchant As WsMerchant In data
        ' Do logic here to map each of the fields in the WsMerchant class 
        ' to the corresponding Merchant class fields
        Dim theMappedMerchant As New Merchant
        theMappedMerchant.Name = theMerchant.Name


        ' Add mapped Merchant (Merchant) to the list
        MappedData.Add(theMappedMerchant)
    Next

    ' Return the mapped list of Merchant objects
    Return MappedData
End Function