mysql: System.Data.SqlTypes.SqlNullValueException on empty string param

vendredi 8 juillet 2016

In my query is this line

//query...
"AND (@4 = '' OR (p.FirstName + p.LastName LIKE '%' + @4 + '%') OR (eup.FirstName + eup.LastName LIKE '%' + @4 + '%')) " +
//more query...

This is giving me a Data is null exception. Param @4 is coming in as "". When I changed this to

"AND (@4 IS NULL OR (p.FirstName + p.LastName LIKE '%' + @4 + '%') OR (eup.FirstName + eup.LastName LIKE '%' + @4 + '%')) " +

It is not returning records that don't have a firstname or lastname in either table.

How can I address this? If param 4 is empty I want to return all records regardless of the name existing or not.

mysql