Question

为什么TryCast不接受t作为Type？

Private Async Function DeSerialize(FilePath As String, t As Type) As Task(Of Object)
  Dim ReadStream = Await Windows.ApplicationModel.Package.Current.InstalledLocation.OpenStreamForReadAsync(FilePath)
  Dim Sarjoittaja As New Runtime.Serialization.DataContractSerializer(GetType(UITextsClass))
  Return TryCast(Sarjoittaja.ReadObject(ReadStream), t)
End Function

仍然没有那么多：

Public Async Function DeSerialize(Of T)(FilePath As String) As Task(Of T)
  Dim ReadStream = Await Windows.ApplicationModel.Package.Current.InstalledLocation.OpenStreamForReadAsync(FilePath)
  Dim Sarjoittaja As New Runtime.Serialization.DataContractSerializer(T) 'T' is a Type and cannot be used as an expression
  Return DirectCast(Sarjoittaja.ReadObject(ReadStream), T)
End Function

Answer 1

您使用Generic Type的语法有点偏差： - 您需要在参数之前定义泛型类型并返回此类型，如下所示：

Private Async Function DeSerialize(Of T)(FilePath As String) As Tasks.Task(Of T)
    'Read and Deserialize
    Dim ReadStream = Await Windows.ApplicationModel.Package.Current.InstalledLocation.OpenStreamForReadAsync(FilePath)
    Dim Sarjoittaja As New Runtime.Serialization.DataContractSerializer(GetType(UITextsClass))
    Return TryCast(Sarjoittaja.ReadObject(ReadStream), T)
End Function

有关详细信息，请参阅docs on MSDN

Answer 2

TryCast运算符以及CType和DirectCast对类型名称而不是System.Type的实例进行操作。

如果您的基础设施允许，请将此方法转换为通用方法。

Private Async Function DeSerialize(Of T)(FilePath As String) As Task(Of T)
 'Read and Deserialize
 Dim ReadStream = Await Windows.ApplicationModel.Package.Current.InstalledLocation.OpenStreamForReadAsync(FilePath)
 Dim Sarjoittaja As New Runtime.Serialization.DataContractSerializer(GetType(UITextsClass))
 Return TryCast(Sarjoittaja.ReadObject(ReadStream), T)
End Function

回复：评论

我不确定这是否是您要问的内容，但您可以使用GetType()运算符获取传入的类型。

Dim t As Type = GetType(T)
Dim Sarjoittaja As New Runtime.Serialization.DataContractSerializer(t)

在VB中尝试使用TypeOf

2 个答案: