Hi
i just started looking into this today and i think i understand it but the example from microsoft that i was learning from has the usual extra stuff that doesnt really need to be there. and im having a hard time getting my head around it
just for practice i want to hard code the 'part' since i know how to get the parts from files already.
this is what i have so far
1 form with 1 datagridview 1 textbox 1 button
i want to put a path to an xl file press the button and let the 'part' start an oledb connection read the xl file close connection and then send the object back
(as an object since i may use it for other types later) oledb is not a problem i can do that, its purely the MEF side of things.
so... the code haha wait for it
and then i got stuck with the way microsoft showed it all on msdn
this i think i need but it has parts of the calculator example on it <below>
and i need to strip the code here to start the 'Part' that i actually need to use, but it looks like theres more interfaces then i actually need, im not sure the example used a console heres some more <below>
heres the interfaces and 1 of the parts <below>
please help :), i understand what is happening a little
but i never used an interface before but i looked it up i think i get that, why are they using so many though
the import/export i understand is checking if the 'part' is allowed to be used, i dont understand the syntax though for them both,
i know someone who has done this should easily help me out here.
i just started looking into this today and i think i understand it but the example from microsoft that i was learning from has the usual extra stuff that doesnt really need to be there. and im having a hard time getting my head around it
just for practice i want to hard code the 'part' since i know how to get the parts from files already.
this is what i have so far
1 form with 1 datagridview 1 textbox 1 button
i want to put a path to an xl file press the button and let the 'part' start an oledb connection read the xl file close connection and then send the object back
(as an object since i may use it for other types later) oledb is not a problem i can do that, its purely the MEF side of things.
so... the code haha wait for it
Code:
Public module module1
public interface IGetFileData
Function GetFileData(fullpath as string)as object
end interface
<a program class i think needs to go here, its shown below, which will be instantiated when i press the button i think>
end modulethis i think i need but it has parts of the calculator example on it <below>
Code:
Public Class Program
Dim _container As CompositionContainer
<Import(GetType(ICalculator))>
Public Property calculator As ICalculator
Public Sub New()
'An aggregate catalog that combines multiple catalogs
Dim catalog = New AggregateCatalog()
'Adds all the parts found in the same assembly as the Program class
catalog.Catalogs.Add(New AssemblyCatalog(GetType(Program).Assembly))
'IMPORTANT!
'You will need to adjust this line to match your local path!
catalog.Catalogs.Add(New DirectoryCatalog("C:\Users\Main Admin\Documents\Visual Studio 2010\Projects\MEF Calculator\SimpleCalculator2\Extensions"))
'Create the CompositionContainer with the parts in the catalog
_container = New CompositionContainer(catalog)
'Fill the imports of this object
Try
_container.ComposeParts(Me)
Catch ex As Exception
End Try
End Sub
End ClassCode:
<Export(GetType(ICalculator))>
Public Class MySimpleCalculator
Implements ICalculator
<ImportMany()>
Public Property operations As IEnumerable(Of Lazy(Of IOperation, IOperationData))
Public Function Calculate(ByVal input As String) As String Implements ICalculator.Calculate
Dim left, right As Integer
Dim operation As Char
Dim fn = FindFirstNonDigit(input) 'Finds the operator
If fn < 0 Then
Return "Could not parse command."
End If
operation = input(fn)
Try
left = Integer.Parse(input.Substring(0, fn))
right = Integer.Parse(input.Substring(fn + 1))
Catch ex As Exception
Return "Could not parse command."
End Try
For Each i As Lazy(Of IOperation, IOperationData) In operations
If i.Metadata.Symbol = operation Then
Return i.Value.Operate(left, right).ToString()
End If
Next
Return "Operation not found!"
End Function
Private Function FindFirstNonDigit(ByVal s As String) As Integer
For i = 0 To s.Length
If (Not (Char.IsDigit(s(i)))) Then Return i
Next
Return -1
End Function
End Classheres the interfaces and 1 of the parts <below>
Code:
Public Interface ICalculator
Function Calculate(ByVal input As String) As String
End Interface
Public Interface IOperation
Function Operate(ByVal left As Integer, ByVal right As Integer) As Integer
End Interface
Public Interface IOperationData
ReadOnly Property Symbol As Char
End Interface
<Export(GetType(IOperation))>
<ExportMetadata("Symbol", "+"c)>
Public Class Add
Implements IOperation
Public Function Operate(ByVal left As Integer, ByVal right As Integer) As Integer Implements IOperation.Operate
Return left + right
End Function
End Classbut i never used an interface before but i looked it up i think i get that, why are they using so many though
the import/export i understand is checking if the 'part' is allowed to be used, i dont understand the syntax though for them both,
Code:
<Export(GetType(IOperation))>
<ExportMetadata("Symbol", "+"c)>
<ImportMany()>
Public Property operations As IEnumerable(Of Lazy(Of IOperation, IOperationData))