How can this be achieved in LINQ ?

Question

I want to rewrite this, maybe using predicates, or Lambda, how can I do this?

        serviceResponse = client.Authorize(....);


        string authorizeResponse = string.Empty;

        foreach (CdcEntry element in serviceResponse.Cdc)
        {
            authorizeResponse += element.Name + Environment.NewLine;
            foreach (CdcEntryItem item in element.Items)
            {
                authorizeResponse += " (" + item.Key + ", " + item.Value + ") " 
                + Environment.NewLine;
            }
        }

Thanks

Answer 1

You certainly could but all you would gain would be a couple of ForEach method calls and multi-statement lambdas inside which (in my opinion) would be significantly less readable.

Without knowing the datatypes of you identifiers (specifically serviceResponse.Cdc and element.Items) you may even have to roll your own ForEach extension method as well to make this work.

I think what you have is better than a LINQ equivalent but if you really want to LINQify it, please post some more info about the code you have posted and we may be able to help more.

Answer 2

I don't think there's any real point to use LINQ here, since you're trying to build a response string, and are thus performing a task most suited to imperative rather than functional programming. (You could of course use the Aggregate method on a string, but that's not really any help.)

In addition, the StringBuilder type is more suited for this sort of job. (It's much more efficient, and also cleaner in my opinion. Of course, the former may not matter so much depending on the context.)

Here is the optimal way to do this, in my view:

serviceResponse = client.Authorize(....);

var sb = new StringBuilder();

foreach (CdcEntry element in serviceResponse.Cdc)
{
    sb.AppendLine(element.Name);
    foreach (CdcEntryItem item in element.Items)
    {
        sb.AppendFormat(" ({0}, {1}) ", item.Key, item.Value);
        sb.AppendLine();
    }
}

var authorizeResponse = sb.ToString();

Answer 3

This should roughly do it:

x = x.Aggregate("",
    (cdc, s) => s + string.Format("{0}{1}",
                    cdc.Name, Environment.NewLine) +

        cdc.Aggregate("",
           (item, s) => s + string.Format(" ({0}, {1}) {2}",
                            item.Key, item.Value, Environment.NewLine)));

Frankly, I am a big functional guy, but multiple nested folds makes me think too hard for a simple problem like this, especially with C#'s verbose syntax. I would not even use this. I would use your foreach version.

Answer 4

You could gain a lot by using string builder instead of string concatenation. Dont see any performance benefit in LINQification.

 StringBuilder sb = new StringBuilder()

 foreach (CdcEntry element in serviceResponse.Cdc)
 {
     sb.AppendLine(element.Name);
     foreach (CdcEntryItem item in element.Items)
     {
        sb.AppendLine(" ({0},{1}) ", item.Key, item.Value);
      }
 }

Answer 5

You can certainly use LINQ to fold the list. But you should keep in mind that language features like LINQ are there to make things simpler and clearer. I'm not sure the logic below is either:

StringBuilder sb = new StringBuilder();
string authorizeResponse = serviceResponse.Aggregate( sb, 
                              (q,x) => q.Append( string.Format( "{0}{1}{2}", x.Name, Environment.NewLine,
                              x.Aggregate( q, (y,z) => y.Append( string.Format("({0}){1}", z.Key, Environment.NewLine) ) ) );

string authorizeResponse = sb.ToString();

Answer 6

        var result =
                elements.Select(
                        element =>
                        new[] {element.Name}.Concat(
                                element.Items.Select(item => "({0},{1})".With(item.Key, item.Value)))).SelectMany(
                        item => item).Join(Environment.NewLine);