Query data with case-insensitivity string comparison in Linq

When building a custom email duplication detection, I need to query all records that match an input email ignoring case. I tried following approaches:

• String.Equals with the second parameter StringComparison.OrdinalIgnoreCase:

Where(p => p.new_Email.Equals(txtEmail, StringComparison.OrdinalIgnoreCase))

• Transform values to lower case before comparison:

Where(p => p.new_Email.ToLower().Equals(txtEmail.ToLower()))

Both attempts threw an exception

“Invalid ‘where’ condition. An entity member is invoking an invalid property or method.”

That’s because the Linq provider can’t translate the query to a valid QueryExpression which should match FetchXML conditional operators.

Interestingly, string comparison in QueryExpression ignores case by default, so Where(p => p.new_Email.Equals(txtEmail)) will work as we want.

For the other way around, if you want case sensitivity, you should add your logic to compare the result(s) of the query with your string.

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