Nesting a LINQ query inside a where clause of another query

How would I combine the following two queries into a single query?

    using (var ctx = ContextFactory.CreateDbContext())
    {
        int parentId = await ctx.MenuEntity.Where(m => m.Title == thisVariable).Select(m => m.MenuId).SingleAsync();
        menuEntityList = await ctx.MenuEntity.Where(m => m.ParentId == parentId).ToListAsync();
    }

Combine two LINQ queries in C#

You can do it by using Join in LINQ.

Code Example:

using (var ctx = ContextFactory.CreateDbContext())
{
   menuEntityList = await (
        from m in ctx.MenuEntity
        where m.ParentId == ctx.MenuEntity
            .Where(x => x.Title == thisVariable)
            .Select(x => x.MenuId)
            .Single()
        select m
   ).ToListAsync();
}

However as you can see the code does not provide a huge advantage and I guess both options probably same in almost every perspective.

A slightly different syntax from the answer by @AztecCodes, more like an IN in SQL

using (var ctx = ContextFactory.CreateDbContext())
{
   menuEntityList = await (
        from m in ctx.MenuEntity
        where ctx.MenuEntity
            .Where(x => x.Title == thisVariable)
            .Select(x => x.MenuId)
            .Contains(m.ParentId)
        select m
   ).ToListAsync();
}

This query is equivalent to EXISTS in sql

 var menuEntityList = context.MenuEntity.Where(
 m => context.MenuEntity.Where(m =>
 m.Title == thisVariable).Any(d => d.MenuId == m.ParentId)
                ).ToList();

I get Query with Profiler

exec sp_executesql N'SELECT [m].[Id], [m].[MenuId], [m].[ParentId], [m].[Title]
FROM [MenuEntity] AS [m]
WHERE EXISTS (
    SELECT 1
    FROM [MenuEntity] AS [m0]
    WHERE [m0].[Title] = @__thisVariable_0 
	AND [m0].[MenuId] = [m].[ParentId])'
,N'@__thisVariable_0 nvarchar(4000)',@__thisVariable_0=N'Org'