Object reference not set to an instance of an object

+ ex {"Object reference not set to an instance of an object."} System.Exception

Solution:
Dim command As New SqlCommand()
Dim hash As New Hashtable
SelectControl.Items.Clear()
Try
hash = ExecuteReader("PRZ3_GetTable", command)
Dim i As Int32
For i = 0 To hash.Count - 1 Step 1
SelectControl.Items.Add(CType(hash(i), ListItem))
Next
SelectControl.DataBind()
Catch ex As Exception
Response.Write(ex.Message)
End Try

因为我For i = 0 To hash.Count -1Step 1原来是For i = 0 To hash.Count Step 1,多了一项
索引是从开始的