CODEWITHSUNDEEP
c#vbacommarshallingtlb
Nitheen Rao
Nitheen Rao

Reputation: 210

String Array property in COM Class and set it from VBA

I am recently working with one type library requirement. I have created a c# class that will be exposed to COM component. However, when I set a value to an array property I get a compiler error. All the code are placed here.

Looking forward to your expert comments!

(VBA) Compile error:
Function or interface marked as restricted, or the function uses an Automation type not supported in Visual Basic

C# Com Class

[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(_LeafletTestClass))]
[ProgId("Leaflet.WebService.Toolkit.LeafletWS.LeafletTestClass")]
[Guid("364C5E66-4412-48E3-8BD8-7B2BF09E8922")]
public class LeafletTestClass : _LeafletTestClass
{
    [ComVisible(true)]
    public string[] TestArrayString
    {
        [return: MarshalAs(UnmanagedType.SafeArray)]
        get;
        [param: MarshalAs(UnmanagedType.SafeArray)]
        set;
    }

}

[ComVisible(true)]
[Guid("8C034F6A-1D3F-4DB8-BC99-B73873D8C297")]
public interface _LeafletTestClass
{
    [ComVisible(true)]
    string[] TestArrayString
    {
        get;
        set;
    }
}

VBA Create Object

Sub test()

Dim testClass As LeafletTestClass
Set testClass = New LeafletTestClass
Dim arr(0 To 1) As String
arr(0) = "Test value"
testClass.TestArrayString = arr

End Sub

Upvotes: 1

Views: 351

Answers (1)

this
this

Reputation: 1426

I would recommend that you avoid using arrays. While you can use Marshal and possibly marshal it across it is fraught with issues due to difference in how empty arrays and nulls are handled, etc. etc.

To avoid runtime errors, you are better off writing a collection class and marshaling that across so that VBA can then simply enumerate. For an example of this, see here

At minimum your collection interface need to look like this:

[
    ComVisible(true),
    Guid(<some guid>),
    InterfaceType(ComInterfaceType.InterfaceIsDual)
]
public interface IDeclarations : IEnumerable
{
    [DispId(0)]
    Declaration Item(int Index);

    [DispId(1)]
    int Count { get; }

    [DispId(-4)]
    IEnumerator _GetEnumerator();
 }

Upvotes: 3

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