Created Unassigned: Analysis.Slope.getslope produce a strange result? [25258]

Dear all,
I use Analysis.Slope.getslope to produce Slope raster but I got a strange result:

- All value in Result Raster is zero
- Cell size in Result Raster is 1x1 (In the Input Raster (DEM) the cell size was 30x30)
- Extent (Bounds) go so far from Input Raster.

Is it a bug? Could you please help me to solve the problem?

Here is the source code (In VB.net)


Dim inputRaster As DotSpatial.Data.IRaster
inputRaster = DotSpatial.Data.Raster.Open("C:\DEM.tif")

Dim rasteroptions As String()
Dim datatype As System.Type = System.Type.GetType("System.Double")
Dim outputRaster As DotSpatial.Data.IRaster
outputRaster = Raster.CreateRaster("C:\slope.tif", Nothing, inputRaster.NumColumns, inputRaster.NumRows, 1, datatype, rasteroptions)
outputRaster.Bounds = inputRaster.Bounds.Copy()
outputRaster.NoDataValue = inputRaster.NoDataValue
outputRaster.Projection = inputRaster.Projection

Slope.GetSlope(inputRaster, 1, true, outputRaster, Nothing)
outputRaster.Save()