This issue took me a day to figure out! Hopefully the tips below will help someone else. I've found that it is caused by one of three things:

1. You modified the size of a column in your database but did not update the 'MaxLength' property column your visual studio project (data designer/ xsd file.

2. You have a mismatch between a column's type in your database and it's type in your visual studio project.

3. The number of columns in your TableAdapter "SELECT" query does not match the number of columns being returned by the "SELECT" query which is causing the exception.

I found following articles useful in solving this problem:

• http://bloggingabout.net/blogs/egiardina/archive/2007/04/11/failed-to-enable-constraints-error-and-the-zen-of-datasets.aspx
• http://www.objectsharp.com/cs/blogs/dave/archive/2003/11/07/188.aspx
• http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=870567&SiteID=1

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