Question

I have used the ‘select’ keyword and extension method to return an IEnumerable<T> with LINQ, but I have a need to return a generic Dictionary<T1, T2> and can’t figure it out. The example I learned this from used something in a form similar to the following:

IEnumerable<T> coll = from x in y      select new SomeClass{ prop1 = value1, prop2 = value2 }; 

I’ve also done the same thing with extension methods. I assumed that since the items in a Dictionary<T1, T2> can be iterated as KeyValuePair<T1, T2> that I could just replace ‘SomeClass’ in the above example with ‘new KeyValuePair<T1, T2> { ...‘, but that didn’t work (Key and Value were marked as readonly, so I could not compile this code).

Is this possible, or do I need to do this in multiple steps?

Thanks.

Answer 1

The extensions methods also provide a ToDictionary extension. It is fairly simple to use, the general usage is passing a lambda selector for the key and getting the object as the value, but you can pass a lambda selector for both key and value.

class SomeObject {     public int ID { get; set; }     public string Name { get; set; } }  SomeObject[] objects = new SomeObject[] {     new SomeObject { ID = 1, Name = "Hello" },     new SomeObject { ID = 2, Name = "World" } };  Dictionary<int, string> objectDictionary =      objects.ToDictionary(         o => o.ID,          o => o.Name); 

Then objectDictionary[1] Would contain the value "Hello"