带有Automapper的泛型-返回单个记录

Question

我有一些这样的代码:

Public Function MakeDatareaderList(Of I As New)(ByVal objDR As DbDataReader) As List(Of I)
            Dim list As List(Of I)
            Mapper.CreateMap(Of DbDataReader, List(Of I))()
            list = Mapper.Map(Of SqlDataReader, List(Of I))(CType(objDR, SqlDataReader))
            Return list
        End Function

按预期工作，即传入一个类型，然后返回该类型的列表。我可以这样做吗?

Public Function MakeDatareaderFirst(Of I As New)(ByVal objDR As DbDataReader) As I
            Mapper.CreateMap(Of IDataReader, IEnumerable(Of I))()
            I = Mapper.Map(Of IDataReader, IEnumerable(Of typeUSN))(objDR).First()
            Return I
        End Function

在上面的代码中，错误是:I不能用作表达式。上面的代码返回一个填充了数据的对象。

Answer 1

您还没有创建一个变量来分配映射器函数的结果给您吗?您试图将其分配给类型I

Public Function MakeDatareaderFirst(Of I As New)(ByVal objDR As DbDataReader) As I
    Dim instance as I
    Mapper.CreateMap(Of IDataReader, IEnumerable(Of I))()
    instance = Mapper.Map(Of IDataReader, IEnumerable(Of I))(objDR).First()
    Return instance
End Function