There is already an open DataReader associated with this Command which must be closed first

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This error occur if you forgot to include “MultipleActiveResultSets=True” in your connection string. It was actually on by default in VS 2005 but was later set to off.

Here’s an example of a connection string w/ MARs set.

SQL Server authentication:

cnString =

"Data Source="

&

ServerName &

";Initial Catalog="

&

DatabaseName &

";Persist Security Info=True;MultipleActiveResultSets=True;User ID=sa;Password=12345678"

Windows Authentication Mode:

cnString =

"Data Source="

&

ServerName &

";Initial Catalog="

&

DatabaseName &

";Integrated Security=True;MultipleActiveResultSets=True"