I created some ArcObjects code that creates a geoprocessing tool that creates a featureclass from some input files. The code creates a GP tool that works as it should, except for one problem: the GP parameter for the input files accepts all files when it is supposed to only accept files with the extension .jxl or .xls.
There is no documentation on how to do this, but below is the code snippet of what I wrote to create the input file parameter. I've also converted the tool to a Python tool (which has much better documentation) and it does filter input files to just the allowed ones. I assume the underlying objects are the same for the .Net SDK as for ArcPy, so there should be a way to get the .net authored tool to work as well. I also looked for clues in the Pro SDK, but came up with nothing since Pro doesn't even support creating GP tools with .net.
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parameter = New GPParameterClass()
Dim inputType As IGPDataType = New DEFileTypeClass()
Dim pGXFileFilter As IGxFileFilter = New GxFileFilterClass
pGXFileFilter.AddFileType("jxl", "Trimble JXL Files", "")
pGXFileFilter = New GxFileFilterClass
pGXFileFilter.AddFileType("xls", "Excel Files", "")
Dim pGXFilterInfo As IGxFilterInfo
pGXFilterInfo = CType(inputType, IGxFilterInfo)
pGXFilterInfo.OpenGxObjectFilters.Add(pGXFileFilter)
pGXFilterInfo.SaveGxObjectFilters.Add(pGXFileFilter)
Dim mvType As IGPMultiValueType = New GPMultiValueTypeClass()
mvType.MemberDataType = inputType
Dim mvValue As IGPMultiValue = New GPMultiValueClass()
mvValue.MemberDataType = inputType
parameter.Name = "input_files"
parameter.DisplayName = "Input Files"
parameter.ParameterType = esriGPParameterType.esriGPParameterTypeRequired
parameter.Direction = esriGPParameterDirection.esriGPParameterDirectionInput
parameter.DataType = CType(mvType, IGPDataType)
parameter.Value = CType(mvValue, IGPValue)
pParameters.Add(parameter)
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