How to import file into gridview in C# windows?

I assume that datagrid and datagridview are the same.

1. Read record / line from file.
2. Parse the record / line and create a datagridviewrow from it.
3. Add the datagridviewrow to the datagridview.
4. Next record / line.
   

You don't give information about the type of input file; fixedwidth, csv, xml, ... So this is just a global approach. You can fill in the details.