Vb.Net 分配给元组

Question

Does VB support assignment to a tuple? If so what is the Syntax?

Private Function GetPeStream(metadataDiagnostics As DiagnosticBag, peStreamProvider As EmitStreamProvider, metadataOnly As Boolean) As (peStream As Stream, signingStream As Stream, selectedStream As Stream)
    Return ...
End Function

Dim ret As Stream
Dim peStream as Stream
Dim signingInputStream as Stream
(peStream, signingInputStream, ret) = GetPeStream(metadataDiagnostics, peStreamProvider, metadataOnly)

Answer 1

You can use below syntax for tuples to initialize and assign in single line.

Dim x As Tuple(Of Stream, Stream, Stream)= New Tuple(of Stream,Stream,Stream)(str1,str2,str3)

Important : Make sure you have str1 , str2 and str3 instantiated and assigned to values before direct assignment above

Answer 2

You can avoid using Item1, Item2, etc, using the example bellow.

Private Function GetPeStream(metadataDiagnostics As DiagnosticBag, peStreamProvider As EmitStreamProvider, metadataOnly As Boolean) As (peStream As Stream, signingStream As Stream, selectedStream As Stream)
    
    .....
    Return (processed_peStream, processed_signingStream,processed_selectedStream)
End Function


Private Function ConsumingGetPeStream()...

    'Calling the function
    Dim Your_Result_From_GetPeStream = GetPeStream(metadataDiagnostics_value, peStreamProvider_value, metadataOnly_Value)
    
    'Using returned values from function    
    Your_Result_From_GetPeStream.peStream
    Your_Result_From_GetPeStream.signingStream
    Your_Result_From_GetPeStream.selectedStream
    

End Function

A more simple version for better undesrtanding

      Public Sub Main()

                Dim ReturnFunctionWithTuple = FunctionWithTuple()

                Console.WriteLine($"Your long: {ReturnFunctionWithTuple.YourFieldLong}")
                Console.WriteLine($"Your date: {ReturnFunctionWithTuple.YourFieldDate}")
                Console.WriteLine($"Your bool: {ReturnFunctionWithTuple.YourFiedBoolean}")


            End Sub

            Public Function FunctionWithTuple() As (YourFieldLong As Long, YourFieldDate As Date, YourFiedBoolean As Boolean)

                Return (55, #01/01/2021#, False)

            End Function

Answer 3

Declare the tuple variable and the function return type with the generic syntax, so that the types line up. For example:

Public Sub GetTuple()
    Dim x As Tuple(Of String, String, Integer)
    x = GetData()
End Sub

Public Function GetData() As Tuple(Of String, String, Integer)

    Dim y = New Tuple(Of String, String, Integer)("A", "B", 27)
    Return y

End Function

Answer 4

In order to do it you have to create a new Tuple that accepts the assignment as shown by PKing and then manually copy each variable one at a time.

Dim x As Tuple(Of Stream, Stream, Stream)
x = GetData()
Dim eStream  as Stream = x.Item1
Dim signingInputStream as Stream = x.Item2
Dim Ret as Stream = x.Item3

Of course the assignments would be in a loop and have code dealing with the types.