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Article ID: 311522 - Last Review: March 9, 2006 - Revision: 1.4
BUG: You cannot create calculated expressions on DataSet objects in the Schema Designer
This article was previously published under Q311522
This article refers to the following Microsoft .NET Framework Class Library namespace:
SYMPTOMS
- When you add an instance of a calculated expression in the Schema Designer and you preview that expression, the following error message appears and you are not allowed to create the instance.
Exception has been thrown by the target of an invocation
- When you modify a DataSet object to add a calculated expression, the form will not load and the Form Designer will display the following error message:
An exception occurred while trying to create an instance of DataSet
CAUSE
The
DataSet tries to use rows that have not yet been defined to create the expression.
RESOLUTION
To work around this problem, create the expressions
after you instantiate the
DataSet. After you create the tables and rows in the
DataSet constructor, the expressions will be accepted. For example:
Dim objDS as new DataSet1
objDS.myTable.AvgColumn.Expression = "avg(Child.Values)"
STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.
APPLIES TO
- Microsoft ADO.NET (included with the .NET Framework)
- Microsoft .NET Framework 1.1
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