Accepted answer

union only works with the same element type. you could use:

var data = => new { p.value1, p.value2 })
     .union( => new { q.value1, q.value2 })
     .union( => new { value1 = r.alias1, value2 = r.other }); 

here the anonymous type serves as a common type to project all three tables onto, so that union can work.

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