Question

注:我不想区分通用参数是否无效。我想知道,如果是is,哪些是不可否认的原始类型?

我在此试图:

Function CreateTdParameter(Of T)(Name As String, Value As T) As TdParameter

    Dim TdType As TdType
    Dim ValueType As Type = GetType(T)

    If ValueType.IsGenericType Then
        Dim GenType As Type = ValueType.GetGenericTypeDefinition()
        If GenType = GetType(Nullable(Of )) Then
            ValueType = Activator.CreateInstance(GenType.MakeGenericType(New Type() {ValueType}))
            ValueType = Nullable.GetUnderlyingType(ValueType.GetGenericTypeDefinition().UnderlyingSystemType)
        End If
    End If

    If ValueType = GetType(String) Then
        TdType = Teradata.Client.Provider.TdType.VarChar
    ElseIf ValueType = GetType(Integer) Then
        TdType = Teradata.Client.Provider.TdType.Integer
    ElseIf ValueType = GetType(DateTime) Then
        TdType = Teradata.Client.Provider.TdType.Timestamp
    Else
        Throw New NotImplementedException(String.Format("{0} not expected.", Value.GetType))
    End If

    Return CreateTdParameter(Name, Value, TdType, ParameterDirection.Input)

End Function

当<代码>Datetime?通过时,便会产生以下错误。价值参数:



GenericArguments[0],  System.Nullable1[System.DateTime] , on  System.Nullable1[T]  violates the constraint of type  T .

看来,我需要找到基本类型,以便用反思来立即消除这种类型。 无法确定如何绕过这一渔获量。

任何人能否向我指出,我可以说明某种通用类型是否无效,如果是,我如何能够获得其基本类型?

Answer 1

例如:

Type underlyingType = Nullable.GetUnderlyingType(typeof(T));
if(underlyingType != null) {
    .. is nullable, with underlying-type as described
}

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