Question

I just want any value where the id equals a “zj”

Dictionary<string,string> z = dm.UpdateAndReturnIdol(User, id, v).where(keys.equals("zj"));

Answer 1

If the return type is Dictionary<string, string> then you can just look up the value, e.g.

Dictionary<string, string> dictionary =  dm.UpdateAndReturnIdol(User, id, v);
string value = dictionary["zj"];

or if you don’t know whether there will be an entry:

Dictionary<string, string> dictionary =  dm.UpdateAndReturnIdol(User, id, v);
string value;
if (dictionary.TryGetValue("zj", out value))
{
    // Use the value
}

There’s no need to use Where here – the whole point of a dictionary is that you can look up by key efficiently… and there can only be one value per key, so there’s no need to get a sequence of values.