Question

I am trying to gransp wether I can get big refactoring advantages out of learning LINQ.
How can LINQ improve this code, which is a real-world example that is representative for a lot of code in a project I work on:

foreach (SchemeElement elem in mainDiagram.Elements)
{
    if (elem.SubType == EElemSubType.BusBar)
    {
        if (connPts.Busbars.ContainsKey(elem.ConnectionPointId))
        {
            if (!taAddrList.TAAddressList.ContainsKey(elem.Key))
            {
                taAddrList.TAAddressList.Add(elem.Key, new TAAddress());
            }

            taAddrList.TAAddressList[elem.Key] = connPts.Busbars[elem.ConnectionPointId];                        
        }
    } // if busbar
} // foreach element

For Clarity:

taAddrList.TAAddressList is of type Dictionary<ElemKey, TAAddress>
where ElemKey is a two-component type that consists of two int ID’s.

connPts.Busbars is of type Dictionary<int, TAAddress>

Answer 1

See for yourself:

var query = from element in mainDiagram.Elements
            where element.SubType == EElemSubType.BusBar
            where connPts.Busbars.ContainsKey(element.ConnectionPointId)
            select element;

foreach (var element in query)
{
    // by accessing immidiatly in a dictionary (assuming you are using one), you can either insert or update 
    taAddrList.TAAddressList[element.Key] = connPts.Bushbars[elem.ConnectionPointId];
}