Index was outside the bounds of the array vb.net n mapwingis

问题

I am making a map app with VB.net and Mapwingis. I want to save the map data with an array, but any error. this code :

 Dim scheme As New MapWinGIS.ColorScheme

    Dim idx As Integer
    idx = FormMain.TreeViewLayer.Nodes.IndexOf(FormMain.TreeViewLayer.SelectedNode)
    sf = FormMain.AxMapMain.get_Shapefile(idx)
    mainMapHandler = FormMain.AxMapMain.AddLayer(sf, True)
    sf = FormMain.AxMapMain.get_Shapefile(mainMapHandler)
    Dim fieldName As Integer
    fieldName = CBSymVarNameUnique.SelectedIndex
    sf.Categories.Generate(fieldName, MapWinGIS.tkClassificationType.ctUniqueValues, 0)
    filcol = Convert.ToUInt32(RGB(255, 255, 255))

    filcol2 = Convert.ToUInt32(RGB(0, 0, 255))
    scheme.SetColors(filcol, filcol2)

    Dim nama2() As String = New String() {}
    For i As Integer = 0 To sf.Categories.Count - 1
        Dim category As MapWinGIS.ShapefileCategory = sf.Categories.Item(i)
        nama2(i) = category.Name.Substring(category.Name.IndexOf("=") + 1) 'error here
    Next

Could you help me out here?

回答1:

In this line

 Dim nama2() As String = New String() {}

you declare an array of string without any space to store strings. The Length of this array is zero.

Of course when you write

 nama2(i) = category.Name.Substring(.....)

the code crashes because there is no space to store elements in the array

You need to declare the array with the appropriare space to store the strings that you plan to retrieve

 Dim nama2(sf.Categories.Count-1) As String

However I suggest to use a List(Of String) and add the elements to this list as you need

Dim nama2 = New List(Of String)()
For i As Integer = 0 To sf.Categories.Count - 1
    Dim category As MapWinGIS.ShapefileCategory = sf.Categories.Item(i)
    nama2.Add(category.Name.Substring(category.Name.IndexOf("="))
Next

来源：https://stackoverflow.com/questions/31133178/index-was-outside-the-bounds-of-the-array-vb-net-n-mapwingis

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vb.net

visual-studio-2012