Arithmetic overflow [algorithm conversion from C# to VB.NET]

System.OverflowException was unhandled
  Message=Arithmetic operation resulted in an overflow.
  Source=WindowsApplication4
  StackTrace:
       at WindowsApplication4.Form1.Crashit() in C:\Users\rx\AppData\Local\Temporary Projects\WindowsApplication4\Form1.vb:line 11
       at WindowsApplication4.Form1.Button1_Click(Object sender, EventArgs e) in C:\Users\rx\AppData\Local\Temporary Projects\WindowsApplication4\Form1.vb:line 24
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
       at WindowsApplication4.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

    Function Crashit()
        Dim a As UInteger, b As UInteger
        Dim k As Integer = 0
        a = InlineAssignHelper(b, &H9E3779B9UI)
        Dim URL As String = "info:google.com"
        Dim length As Integer = URL.Length
        While length >= 12
            a += CUInt(AscW(URL(k + 0))) + CUInt(AscW(URL(k + 1)) << 8) + CUInt(AscW(URL(k + 2)) << 16) + CUInt(AscW(URL(k + 3)) << 24)
        End While
    End Function
    Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, value As T) As T
        target = value
        Return value
    End Function

CUInt(AscW(URL(k + 3)) << 24)

                uint a, b;
                a = b = 0x9E3779B9;
                int k = 0;
                string URL = "info:google.com";
                int length = URL.Length;
                while (length >= 12)
                {
                    a += (uint)(URL[k + 0] + (URL[k + 1] << 8) + (URL[k + 2] << 16) + (URL[k + 3] << 24));
                }