Checking String Value in vb.net

What is the issue in the if clause below??I am getting 'Object reference not set to an instance of an object.'
This is the clause I need to implement    'if Risk Assessment Type is NOT Equal to "ManualUnderwriting" or Null (or Blank), a valid value is required.  '


Dim inRiskAssmtType As String = GetSafeParsedString(Row.inRISKASSMTTYPE).ToUpper()

If Row.inRISKASSMTTYPE_IsNull = True OrElse inRiskAssmtType <>"MANUALUNDERWRITING" Then
                Throw New Exception("  value is required for ,risk assessment type  '" + Row.inRISKASSMTTYPE.ToString() + "'")
            End If

Thanks in advance!!!!