I came across a scenario where I had to use Union all, how can I achieve so in LINQ to entities ?
Here is the answer you are looking for. Use the Concat keyword.
From the example:
var query = (from x in db.Table1 select new {A = x.A, B = x.B}) .Concat( from y in db.Table2 select new {A = y.A, B = y.B} );