Entityframework Join using join method and lambdas

Generally i prefer the lambda syntax with LINQ, but Join is one example where i prefer the query syntax – purely for readability.

Nonetheless, here is the equivalent of your above query (i think, untested):

var query = db.Categories         // source
   .Join(db.CategoryMaps,         // target
      c => c.CategoryId,          // FK
      cm => cm.ChildCategoryId,   // PK
      (c, cm) => new { Category = c, CategoryMaps = cm }) // project result
   .Select(x => x.Category);  // select result

You might have to fiddle with the projection depending on what you want to return, but that’s the jist of it.