How do I use lambda expressions to filter DataRows?

Question

How can I search rows in a datatable for a row with Col1=\"MyValue\"

I\'m thinking something like

Assert.IsTrue(dataSet.Tables[0].Rows.
    FindAll(x =&g         


        

Answer 1

You can use LINQ to DataSets to do this:

Assert.IsTrue(dataSet.Tables[0].AsEnumerable().Where(
    r => ((string) r["Col1"]) == "MyValue").Count() == 1);

Note, you can also do this without the call to Assert:

dataSet.Tables[0].AsEnumerable().Where(
    r => ((string) r["Col1"]) == "MyValue").Single();

If the number of rows does not equal one (hence, the call to Single), then an exception will be thrown, and that unhandled exception should fail your test case. Personally, I like the latter, as it has a clearer semantic meaning.

The above can be further whittled down to:

dataSet.Tables[0].AsEnumerable().Single(
    r => ((string) r["Col1"]) == "MyValue");

Additionally, you can take advantage of the Field method on the DataRowExtensions class to simplify type-safe access to the field (as well as providing the extra benefit of converting DBNull to null counterparts in .NET):

dataSet.Tables[0].AsEnumerable().Single(
    r => r.Field("Col1") == "MyValue");