Grouping by multiple keys known at runtime

Question

I have a telerik grid that I databind a list of objects to on a page. The users can group columns to their liking when viewing the data. I am writing a function to export this data in an excel document and would like to preserve the grouping that the user has on the page. I am able to get the string names of the properties of my objects that the user has grouped by.

What I am stuck on is how to do the grouping during runtime. There are plenty of examples such as this: Group by with multiple columns using lambda describing how to group by multiple properties during compile time when you know ahead of time. I however, do not know what to group by until during run time.

Is there any suggestions on how to go about grouping during runtime?

Answer 1

You're probably looking for something like the answer to this SO question, notably:

var myData = gridData.AsEnumerable()
                     .GroupBy(r => r, new MyDataComparer(keys))
                     .ToList();

internal class MyDataComparer : IEqualityComparer<MyDataType>
{
    private readonly string[] _keys;

    public MyDataComparer(string[] keys)
    {
        _keys = keys; // keep the keys to compare by.
    }

    public bool Equals(MyDataType x, MyDataType y)
    {
        // a simple implementation that checks if all the required fields 
        // match. This might need more work.
        bool areEqual = true;
        foreach (var key in _keys)
        {
            areEqual &= (x[key].Equals(y[key]));
        }
        return areEqual;
    }

    public int GetHashCode(DataRow obj)
    {
        // Add implementation here to create an aggregate hashcode.
    }
}