By using Concat() Or Union()var filter1 = from p in db.table1 var filter2 = from p in db.table2var filter3 = filter1.Concat(filter2); var filter4 = filter1.Union(filter2);Now, what is the difference b/w Concat() & Union() or when we use it?Union removes duplicates. Concat does not.So, they produce different results if the sources either contain any items in common, or have any internal duplicates.If you can guarantee there are no duplicates, or if there are few and you don't care about having them in your output, Concat will be faster since there's no need to test each value against what has already been yielded.However, if there are many duplicates and you don't need them, the extra processing in Union to remove the dupes may be offset by the savings in your code that consumes the results.