Adding more data to a result of a task

Every now and then I need to generate,from an array of data,an array of Tasks and then

await Task.WhenAll(TheTaskArray)

The problem is that I need to consolidate the return data of each array with the original array – to make some modifications.

For  example,in the generator of https://ignatandrei.github.io/RSCG_Examples/v2/docs/category/rscg-examples I do something like this

var t = _AllDescriptions
            .Select(it =>GrabReadMe(it))
            .ToArray();
var data = await Task.WhenAll(t);
//now,for each item in data array I want to put something into original _AllDescriptions

My first try was a simple class

public struct TaskWithData<TData,TResult>//: INotifyCompletion
{
    private readonly TData data;
    private readonly Task<TResult> taskToExecute;
 
    public TaskWithData(TData data,Task<TResult> taskToExecute)
    {
        ArgumentNullException.ThrowIfNull(taskToExecute);
        this.data = data;
        this.taskToExecute = taskToExecute;
    }
# region add this to have Task.WhenAll
    public async Task<( TData data,TResult res)> GetTask() {
        var res = await taskToExecute;
        return (data,res);
    }
    public static explicit operator Task<(TData data,TResult res)>(TaskWithData<TData,TResult> b) 
        => b.GetTask() ;

    #endregion
}

And now the code could be written as

var t = _AllDescriptions.Select(
            it => new TaskWithData<Description,string?>(it,GrabReadMe(it))
            )
            .Select(td=>td.GetTask())            
            .ToArray();

        var desc = await Task.WhenAll(t);
        foreach (var item in desc)
        {
            item.data.Readme = item.res;
        }

But I do not like so much … so 2 iterations with extensions

public static class Extensions
{ 
    #region transform to task
    public static Task<( TData data,TResult res)> AddData<TData,TResult>(this Task<TResult> taskToExecute,TData data)
    {
        var td=new TaskWithData<TData,TResult>(data,taskToExecute);
        return td.GetTask();
    }
    public static Task<(TData data,TResult res)>[] SelectTaskWithData<TData,TResult>(this TData[] arr,Func<TData,Task<TResult>> func) {
        return arr.Select(it => func(it).AddData(it)).ToArray();
    }
    #endregion
}

So now the code becomes

var t = _AllDescriptions
            .Select(it =>GrabReadMe(it).AddData(it))
            .ToArray();

or

var t = _AllDescriptions.SelectTaskWithData(GrabReadMe).ToArray();

It was interesting to create this in order to add more data to the return value of a Task