动态使用查询语法创建LINQ查询表达式的方法有哪些？

Question

What are the possible ways to create a LINQ expression dynamically, but using the query syntax ? Is the query syntax a C# thing only, and if so, is the only viable way of creating such expressions using Roslyn dynamic compilation?

When writing LINQ expressions manually, I find them more natural when written using method chaining syntax, for example ctx.Foo.Where(foo => foo.Type.Name == "Bar") but there are some cases where I would need to write them like this:

from foo in ctx.Foo
join fooType in ctx.Types on foo.TypeId equals fooType.Id
where fooType.Name == "Bar"

I love how expression trees ensure type safety when creating expressions dynamically, but how would one create expressions using the query syntax?

Answer 1

Thanks everyone for your comments. So it turns out it's not possible to do this because query syntax is just a C# language syntactic sugar.

Additionally, if someone else stumbles upon this question, take a look at the excellent answer by @Gert: https://stackoverflow.com/a/15599143/828023

That answer explains that the query syntax is "sugar", while the method syntax shows what really goes on under the hood, where for example join x in y on z equals x.something into somethingElse is actually a GroupJoin method call and there is no way to express this with expression trees without actually calling GroupJoin .