ASP.Net Routing - collection was modified enumeration operation may not execute

Question

I got error randomly on the site as per below error image.

I have used just for loop to add Route to RouteTable and I have clear Routes before alter Route collection.

RouteTable.Routes.Clear()
For i As Integer = 0 To ds.Tables(0).Rows.Count - 1
     RouteTable.Routes.MapPageRoute(Convert.ToString(ds.Tables(0).Rows(i)("routename")), Convert.ToString(ds.Tables(0).Rows(i)("tm_RouteURL")), Convert.ToString(ds.Tables(0).Rows(i)("tm_PhysicalFile")), False, Nothing, Nothing, _
                         New RouteValueDictionary() From { _
                         {Convert.ToString(ds.Tables(0).Rows(i)("tm_ParameterName1")), Convert.ToString(ds.Tables(0).Rows(i)("tm_ParameterValue1"))} _
                        })
Next

I could not figure out why this error is occurred. Anyone knows why this is happening with Routing?

Answer 1

You are trying to alter (add-delete item) a collection during a foreach iteration probably and that's why you get this message.

You can use a list instead and add-remove item through there.