The allowed function parameter and return types are:

• Double
• String
• DateTime -- returns a double to Excel (maybe string is better to return?)
• Double[] -- if only one column is passed in, takes that column, else first row is taken
• Double[,]
• Object
• Object[] -- if only one column is passed in, takes that column, else first row is taken
• Object[,]
• Boolean (bool) -- returns an Excel bool (maybe string is better to return to Excel?)
• Int32 (int)
• Int16 (short)
• UInt16 (ushort)
• Decimal

incoming function parameters of type Object will only arrive as one of the following:

• Double
• String
• Boolean
• ExcelDna.Integration.ExcelError
• ExcelDna.Integration.ExcelMissing
• ExcelDna.Integration.ExcelEmpty
• Object[,] containing an array with a mixture of the above types
• ExcelReference -- (Only if AllowReference=true in ExcelArgumentAttribute causing R type instead of P)

function parameters of type Object[] or Object[,] will receive an array containing a mixture of the above types (excluding Object[,])

return values of type Object are allowed to be:

• Double
• String
• DateTime
• Boolean
• Double[]
• Double[,]
• Object[]
• Object[,]
• ExcelDna.Integration.ExcelError
• ExcelDna.Integration.ExcelMissing.Value // Converted by Excel to be 0.0
• ExcelDna.Integration.ExcelEmpty.Value // Converted by Excel to be 0.0
• Int32 (int)
• Int16 (short)
• UInt16 (ushort)
• Decimal
• otherwise return #VALUE! error

return values of type Object[] and Object[,] are processed as arrays of the type Object, containing a mixture of the above, excluding the array types.

Intended for use within user code (all in the namepace ExcelDna.Integration) are the following:

ExcelFunctionAttribute - for user-defined functions Name Description Category (by default the name of the add-in) HelpTopic IsVolatile (! suffix) IsMacroType (# suffix) ExcelArgumentAttribute - for the arguments of user-defined functions Name Description AllowReference (R type) - Arguments of type object may receive ExcelReference. ExcelCommandAttribute - for macro commands Name Description HelpTopic ShortCut MenuName (default is library name) MenuText IsHidden

ExcelReference - contains a sheet reference. Get/SetValue to read/write to the cells. ExcelError - an enum listing the different Excel errors ExcelDnaUtils - contains Application property (for COM access), WindowHandle and IsInFunctionWizard, ExcelVersion, ExcelLimits.

XlCall class XlCall.Excel wraps Excel4/Excel12 (but easy to call), also constants for all the API functions and commands.

XlCallException - is thrown when the call to Excel fails.

XlCall.TryExcel - does not throw exception on fail, but returns an XlCallReturn enum value. ExcelDna.Integration.Integration contains the static method 'RegisterMethods' which allow dynamic registration of methods.

ExcelDna.Integration.ExcelDnaUtils.Application returns the Excel Application COM object. From VB this can be used late-bound quite easily.

A reference to the ExcelDna.Integration assembly in the .xll file that is loading a .dna file is always added when the .dna file is compiled.

In addition, the following references are added to each project, unless a DefaultReferences="false" attribute is set on the : System.dll System.Data.dll System.Xml.dll

For VB projects, the following imports are added, unless a DefaultImports="false" attribute is set on the : Microsoft.VisualBasic System System.Collections System.Collections.Generic System.Data System.Diagnostics ExcelDna.Integration

DnaLibrary Name Description Language

....

Cleanup is only done when the add-in is removed from the add-in manager. When File->Open is used to reopen the .xll, it is closed and opened, causing the .dna file to be re-read.