DataTable - Dynamic Linq OrderBy using Lambda expressions

Question

DataTable - Dynamic Linq OrderBy using Lambda expressions

.net c# dynamic-linq linq

Question

I'm getting a collection of records in a DataTable and binding it to a grid control. Before binding it I'm sorting the data based on few conditions. For brevity I'm will explain a test scenario.

I've two fields Category and Country. I want to first sort the records based on category and then by country. But the catch here is I want to push all the empty category values to the end and then sort based on the alphabetical order.

For that I'm doing -

var rows = dt.AsEnumerable()
        .OrderBy(r => string.IsNullOrEmpty(Convert.ToString(r["Category"]))) //push empty values to bottom
        .ThenBy(r => Convert.ToString(r["Category"]))
        .ThenBy(r => Convert.ToString(r["Country"]))

But now, the fields based on which I need to sort, is dynamic which I'm having in an array.

How can I use the lambda expressions to order the records dynamically based on the fields? (pushing the empty values to the end)

NLV

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MarcinJuraszek · Accepted Answer · 9/26/2014 1:04:19 AM

I assume the array you're talking about is an array of strings.

var columns = new string[] { "Category", "Country" };

var rows = dt.AsEnumerable().OrderBy(x => 0);
foreach(var columnName in columns)
{
    rows = rows.ThenBy(r => string.IsNullOrEmpty(Convert.ToString(r[category])))
               .ThenBy(r => Convert.ToString(r[category]));
}

Because LINQ uses deferred execution, your query will not be evaluated until you actually need results. That's why you can construct it in multiple steps like in the example above.

DataTable - Dynamic Linq OrderBy using Lambda expressions

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