reference-data-type-marshalling.md

layout	title
page	Excel-DNA Reference: Data type marshaling

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
• Int64 (long)

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
• ExcelDna.Integration.ExcelReference
• Int32 (int)
• Int16 (short)
• UInt16 (ushort)
• Decimal
• Int64 (long)

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.

Special return values

The following invalid return values, are returned to Excel as indicated

• Object[0] => #VALUE
• Object[0.0] => #VALUE
• String.Empty => ""
• ExcelEmpty.Value => 0
• null => #NUM