Question

Here is the starting code:

Dictionary<string,object> dest=...;
IDictionary<string,object> source=...;

// Overwrite in dest all of the items that appear in source with their new values
// in source. Any new items in source that do not appear in dest should be added.
// Any existing items in dest, that are not in source should retain their current 
// values.
...

I can obviously do this with a foreach loop that goes through all of the items in source, but is there some shorthand way to do this in C# 4.0 (perhaps LINQ)?

Thanks

Answer 1

The foreach is pretty small. Why complicate things?

foreach(var src in source)
{
    dest[src.Key] = src.Value;
}

---

If you’re going to repeat this often, you could write an extension method:

public static void MergeWith<TKey, TValue>(this Dictionary<TKey,TValue> dest, IDictionary<TKey, TValue> source)
{
    foreach(var src in source)
    {
        dest[src.Key] = src.Value;
    }
}

//usage:
dest.MergeWith(source);

---

As for doing it “with LINQ”, the query part means that a LINQ method should have no side effects. Having side effects is often confusing to those of us who expect no side effects from it.