EXCEL DNA COM Sample : Generation of an XLL file to be used in VBA.
This is a v2 version, more detailed, of project ExcelDna.COM.QuickStart.

You should know that Excel DNA allows to expose UDF functions under Excel Sheets.

• as formula in cell
• directly via VBA Code with :

Application.Run("[my function name here]")

To do so, these functions are implemented in C# as public static in static class.

Yet besides to this, and more powerful: we will demonstrate any C# functions could be COM exposed. The Goal of the produced XLL is to expose, via COM technology, C# functions which can be used under VBA Excel code.

• Check Post Build event of project "DataApi.XLAddin", this will:
• Generate tlb files
• Build a DataApi.XLAddin-packed.xll.
• Copy DataApi.XLAddin-packed.xll to lib\DataApi.XLAddin.xll (renaming)
• Copy DataApi.XLAddin.xll.config to lib\DataApi.XLAddin.xll.config

tlb files will allow any C# functions to be COM exposed.

• Open Excel
• Load the DataApi.XLAddin.xll.
  Or, Open Excel, Tools > References > Browse in order to add the generated lib\DataApi.XLAddin.xll

In a classical COM registration process, user will need to add tlb as VBA References, then regsvr32 these tlb.
The drawback of this method is that it will register in the personal local registry.

With EXCEL DNA, we do not need to reference the tlb anymore but the .xll:
DataApi.XLAddin.xll contains all the plumbing in the .dna file.
At each use, the xll will register in a personal "on-the-fly" EXCEL DNA virtual env.

What dll is COMVisible:

<ExternalLibrary Path="DataApiXLAddin.dll" ComServer="true" Pack="true" />

Auto-registration routine is implemented in class:

ExcelAddin.cs

• Open Sample "Sheet_Testing_XLL.xlsm" and browse for the xll as shown in step 2.
• Input order parameters and click to book the order.

• log4net.dll is packed in .dna config

<Reference Path="log4net.dll" LoadFromBytes="true" Pack="true" />

• loaded via DataApi.XLAddin > AssemblyInfo.cs file:

[assembly: log4net.Config.XmlConfigurator]

• Files "DataApi.XLAddin.xll.config" and referenced "DataApi.XLAddin.xll" must be in the same directory
• File "DataApi.XLAddin.xll.config" is configured by default to log in directory :

C:\log 

ExcelDna-master\ExcelDna-master\Distribution\Samples\ComServer 

In "AutoDual" mode, we do not need to declare an interface ICOMFooBar to define what will be explicitely COM Visible.
However, default methods such as :
Equals(), GetHashCode(), GetType(), ToString() will appeared as COM Visible and available for use in EXCEL VBA.

A sample class has been written "COMFooBar.cs" for demo purpose:

In order to set the string[] AdditionnalInfos property of Trade class, please check the demonstration in COMTrade class :

public void SetAdditionnalInfos(object addInfosStringArray)    

Call in VBA

Dim additionnalInfosArr(3) As String
...
comTrade.SetAdditionnalInfos (additionnalInfosArr)

Help and details here.