Sort DataTable DataView ascending with null or empty last.

You first need to specify the sorting column in 'param' and replace the original DataTable by 'collection'.

In this example I filter a DataTable with the SelectedValue given by my DropDownList control (ddlFiltre).

In the DataRow array 'nameNotNull' I simply simply the data that are not null for my parameter and sort them.
And in the DataRow array 'nameNull' I select the null data for my parameter.

You just need to merge the two DataRow array and bind it with the GridView

DataTable collection;
//Fill the dataTable
//...
///

protected void ddlFiltre_Change(object sender, EventArgs e){ 
  if (!string.IsNullOrEmpty(ddlFiltre.SelectedValue)) {   
       string param = "Name";
       DataRow[] nameNotNull = collection.Select(string.Format("{0} IS NOT NULL AND {0} <> ''", param),string.Format("{0} ASC", param));
       DataRow[] nameNull = collection.Select(string.Format("{0} IS NULL OR {0} = ''", param));
        DataTable collectionSorted = collection.Clone();

   if (nameNotNull.Length > 0)
   {
      foreach (DataRow dr in nameNotNull)
      {
         DataRow newRow = collectionSorted.NewRow();
         newRow.ItemArray = dr.ItemArray;
         collectionSorted.Rows.Add(newRow);
      }
      if (nameNull.Length > 0)
      {
         foreach (DataRow dr in nameNull)
         {
            DataRow newRow = collectionSorted.NewRow();
            newRow.ItemArray = dr.ItemArray;
            collectionSorted.Rows.Add(newRow);
         }
       }
    }
    else if (nameNull.Length > 0)
    {
       foreach (DataRow dr in nameNull)
       {
          DataRow newRow = collectionSorted.NewRow();
          newRow.ItemArray = dr.ItemArray;
          collectionSorted.Rows.Add(newRow);
       }
    }
    gvItems.DataSource = collectionSorted;
    gvItems.DataBind();
}}