Question

我的xaml表单上有一个列表框，我绑定到List（Of MyType）属性。我这样填写了这个列表：

Dim fields As List(Of CheckableFields) = New List(Of CheckableFields)

    Using context As ITIPEntities = New ITIPEntities()

        Try

            Dim propertyInfoList As List(Of PropertyInfo) = GetType(PC).GetProperties().ToList()

            For Each pI In propertyInfoList
                If (pI.PropertyType <> GetType(EntityState) _
                 And pI.PropertyType <> GetType(EntityKey) _
                 And pI.PropertyType <> GetType(EntityCollection(Of DiskDrive)) _
                 And pI.PropertyType <> GetType(EntityCollection(Of Memory)) _
                 And pI.PropertyType <> GetType(EntityCollection(Of Monitor)) _
                 And pI.PropertyType <> GetType(EntityCollection(Of Network)) _
                 And pI.PropertyType <> GetType(EntityCollection(Of Processor))) Then
                    fields.Add(New CheckableFields(pI.Name))
                End If
            Next

        Catch ex As Exception

        End Try

    End Using

现在，我正处于用户选择他们想要包含在报告中的字段的位置，我需要迭代所需的字段。这是我的linq查询：

For Each checkedField In _requiredFields
                If checkedField.IsChecked Then
                    If checkedField.FieldData IsNot Nothing AndAlso checkedField.FieldData.Trim IsNot String.Empty Then
                        Dim fieldData As String = checkedField.FieldData
                        Dim name As String = checkedField.Name
                        lquery = From comp In lquery Where CType(comp.GetType.GetProperty(name).GetValue(comp, Nothing), String).ToUpper.Contains(fieldData.ToUpper) Select comp
                    End If
                End If
            Next

抛出了linq无法识别GetValue方法的异常。

如何动态获取属性值？

编辑：

我无法找到一种方法来实现Linq to Entities，但我确实找到了一种方法，没有Linq对我有用：

For Each field In _requiredFields
                If field.IsChecked Then
                    reportGenerator.AllFields.Add(field.Name)
                    If field.FieldData IsNot Nothing Then
                        For i As Integer = pcs.Count - 1 To 0 Step -1
                            Dim compPropertyValue As String = CType(pcs(i).GetType().GetProperty(field.Name).GetValue(pcs(i), Nothing), String).ToUpper()
                            If Not compPropertyValue.Contains(field.FieldData.ToUpper()) Then
                                pcs.RemoveAt(i)
                            End If
                        Next i
                    End If
                End If
            Next

Answer 1

LINQ-to-Entities不支持此构造。这是一个设计限制请尝试使用Entity SQL，如以下示例所示：
"SELECT VALUE comp From COMPs AS comp WHERE comp." & name & ".ToUpper().Contains(" & fieldData & ".ToUpper()"

Linq到实体。 GetPropety（名称）.Get值不被linq识别

1 个答案: