This is the syntax (below) to solve the problem after (!IsPostBack).
DataTable dt = new DataTable();
dt.Columns.Add("File");
dt.Columns.Add("Size");
dt.Columns.Add("Type");
foreach (string strfile in Directory.GetFiles(Server.MapPath("../Meow_Directory/")))
{
FileInfo fi = new FileInfo(strfile);
dt.Rows.Add(fi.Name, fi.Length.ToString(),
GetFileType_ByExtension(fi.Extension));
}
FileGrid.DataSource = dt;
FileGrid.DataBind();