Question

I’ve got some code which accepts a DataTable as a parameter and calculates the total of several of the columns in the DataTable. I thought it might be nice to be able to pass in a lambda expression which would perform a filter on the column I’m totaling.

Here’s a portion of the code:

public TrafficTotals CalculateTotals(DataTable table) {     TrafficTotals total = new TrafficTotals();     total.TotalTraffic = table.AsEnumerable().Sum(p => p.Field<int>('Converted'));     // More stuff 

I can manually add a filter into the expression directly in the code:

var filteredTotal = table.AsEnumerable().Where(p => p.Field<string>('MyColumn') == 'Hello').Sum(p => p.Field<int>('Converted')); 

But instead I’d like to pass the ‘Where’ portion as lambda expression instead, but I keep getting lost in the syntax to get the parameters correct.

I have several ways of working around this that don’t really involve lambdas but it seems like a nice way of handling this.

Any ideas?

Answer 1

I’m slightly confused because you’re already specifying the Where clause with a lambda expression, but I suspect you want this:

public TrafficTotals CalculateTotals(DataTable table,                                       Func<DataRow, bool> filter) {     TrafficTotals total = new TrafficTotals();     total.TotalTraffic = table.AsEnumerable()                               .Where(filter)                               .Sum(p => p.Field<int>('Converted'));     // More stuff } 

You’d then call it with:

totals = CalculateTotals(table,                           row => row.Field<string>('MyColumn') == 'Hello'); 

Is that what you’re after?