Vb.net 在LINQ查询中调用用户定义的函数

关于这一点，我在网上看到了一些页面，但不幸的是，示例代码是用C语言编写的。我不能理解其中的大部分（和/或通过代码转换器运行），但我仍然需要帮助使其在VB中工作

我的自定义功能是：

Public Shared Function GetFriendlyTitle(Title As String) As String
    Dim ConvertedTitle As String = ""
    Try
        Dim oRE As Regex = New Regex("[^a-zA-Z0-9\s]")
        ConvertedTitle = Trim(oRE.Replace(Title, "")).Replace(" ", "_")
    Catch ex As Exception
        LogError(ex)
    End Try
    Return ConvertedTitle
End Function 

下面是我调用的返回产品的函数：

Public Shared Function GetProductByTypeAndTitle(URLFriendlyTitle As String, ProductType As ProductType)
    Try
        'don't know why, but the server threw errors if I went c.Type=Type
        Dim pt As Integer = CInt([Enum].Parse(GetType(ProductType), [Enum].GetName(GetType(ProductType), ProductType)))

        Dim context As LionsSharePressEntities = New LionsSharePressModel.LionsSharePressEntities
        return From p In context.Products Where GetFriendlyTitle(p.Title) = URLFriendlyTitle AndAlso p.Type = pt
    Catch ex As Exception
        LogError(ex)
        Return nothing
    End Try
End Function 

它编译得很好，但运行时会挂起。正是返回行完成了此操作。

尝试添加语句：

return From p In context.Products 
           Where GetFriendlyTitle(p.Title) = URLFriendlyTitle 
           AndAlso p.Type = pt 
           Select p

---

这个问题有点老了，似乎已经解决了。但我仍在发布这篇文章，希望它能帮助其他人找到一个对我有效的替代解决方案

另外请注意，我无法在LINQ查询中使用w/调用我的函数，这使我的情况略有不同。我觉得这更有理由发布另一个答案

Public Function GetFriendlyTitle(Title As String) As String
    Dim ConvertedTitle As String = ""
    Try
        Dim oRE As Regex = New Regex("[^a-zA-Z0-9\s]")
        ConvertedTitle = Trim(oRE.Replace(Title, "")).Replace(" ", "_")
    Catch ex As Exception
        LogError(ex)
    End Try
    Return ConvertedTitle
End Function

当我在LINQ查询中遇到从w/调用非共享用户定义函数的问题时，我使用OPs代码片段作为示例解决了这个问题

Public Shared Function GetProductByTypeAndTitle(URLFriendlyTitle As String, _
                                                ProductType As ProductType)
    Try
        'don't know why, but the server threw errors if I went c.Type=Type
        Dim pt As Integer = _
                CInt([Enum].Parse(GetType(ProductType), _ 
                     [Enum].GetName(GetType(ProductType), ProductType)))
        Dim context As New LionsSharePressModel.LionsSharePressEntities

        '// Here is the lambda that will call your GetFriendlyTitle function
        Dim callUserFunc As Func(Of String, String) = _
                Function(title As String)
                    Return GetFriendlyTitle(title)
                End Function

        '// Now call Invoke on the lambda and pass in the needed param(s) from within your LINQ query
        return From p In context.Products _
               Where callUserFunc.Invoke(p.Title) = URLFriendlyTitle AndAlso p.Type = pt

        '//return From p In context.Products Where GetFriendlyTitle(p.Title) = URLFriendlyTitle AndAlso p.Type = pt

    Catch ex As Exception

        LogError(ex)
        Return nothing

    End Try
End Function 

---

我对VB不是很在行，但对我来说，在GetProductByType和Title函数定义中似乎缺少了返回类型。请注意，

GetFriendlyTitle

函数应该是

return ConvertedTitle

，而不是

return Title

。不是吗？你说得对。我刚修好，谢谢！我刚刚尝试了这个方法，结果返回“LINQ to Entities无法识别方法'System.String GetFriendlyTitle（System.String）'方法，并且该方法无法转换为存储表达式。”