Querying DataColumnCollection with LINQ

问题:

I'm trying to perform a simple LINQ query on the Columns property of a DataTable:

from c in myDataTable.Columns.AsQueryable()
    select c.ColumnName

However, what I get is this:

Could not find an implementation of the query pattern for source type 'System.Linq.IQueryable'. 'Select' not found. Consider explicitly specifying the type of the range variable 'c'.

How can I get the DataColumnCollection to play nice with LINQ?

回答1:

How about:

var x = from c in dt.Columns.Cast<DataColumn>()
        select c.ColumnName;

回答2:

You could also use:

var x = from DataColumn c in myDataTable.Columns
        select c.ColumnName

It will effectively do the same as Dave's code: "in a query expression, an explicitly typed iteration variable translates to an invocation of Cast(IEnumerable)", according to the Enumerable.Cast<TResult> Method MSDN article.

回答3:

With Linq Method Syntax:

var x = myDataTable.Columns.Cast<DataColumn>().Select(c => c.ColumnName);