InvalidOperationException: There is already an open DataReader associated with this Command which...

spottedmahn

When I try to run 2 ExecuteQueryDynamic()'s, I get:

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

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sample code:

//works
ExecuteQueryDynamic("SELECT TOP 1 * FROM Customers").Dump();

//doesn't work
ExecuteQueryDynamic("SELECT TOP 1 * FROM Customers").Dump();

reference: https://stackoverflow.com/a/27750602/185123

JoeAlbahari

I can't reproduce this in LINQPad 6 or LINQPad 5. Is it a standard LINQ-to-SQL connection? Is there any other info you can provide?

ssswwn

It seems to make doing the dump in between
//works
var ret = ExecuteQueryDynamic("SELECT TOP 1 * FROM Customers");
ret.Dump();
//doesn't work
var ret2 = ExecuteQueryDynamic("SELECT TOP 1 * FROM Customers");
ret2.Dump();

nescafe

This issue is reproducible in Results to Data Grids mode.

You can solve this by iterating the IEnumerable manually, to make sure each reader is executed once during execution.