Use of C# var for implicit typing of System.Data.Datarow

Question

foreach (var row in table.Rows)
{
     DoSomethingWith(row);
}

Assuming that I\'m working with a standard System.Data.DataTable (which has

Answer 1

table.Rows is a DataRowCollection which is IEnumberable ( and not IEnumerable<T>, T being DataRow), so it is not strongly typed to a DataRow, but a object i.e it is a collection of objects.

There is a DataTable extensions which you can use though - http://msdn.microsoft.com/en-us/library/system.data.datatableextensions.asenumerable.aspx

foreach (var row in table.AsEnumerable())
{

}

Answer 2

That's because Rows is DataRowCollection, which in turn is IEnumerable and not IEnumerable<DataRow>, which means that type inferred will be object.

When you explicitly state type in foreach, you instruct c# to add cast to each call, which is why it works.

Answer 3

An implicit cast happens. Also note that an InvalidCastException can be thrown if the cast isn't possible.