Get Total count of rows in GridView when AllowPaging True in ASP.Net

I am using a grid view and a textbox(out of gridview to display the total rows in gridview) , i am doing Paging in GridView , and pageSize is set to 5 ; so far i did this

 protected void ExistingMappedGrid_OnRowDataBound(object sender, GridViewRowEventArgs e)
    {
        totalRowsLabel.Text = "Total " + ExistingMappedGrid.Rows.Count + " records.";
    }

it shows the number of records , but not total ! it shows only the records displaying on the page .

e.g.

if i have a total of 8 records , not page index works and shows 5 rows in gridview and other 3 rows on 2nd page index , but if on first instane page shows 5 records in gridview then textbox shows 5 and when i click on second page index it shows 3 rows  ( THAT"S NOT WHAT I CODED AND NOT NEEDED ) i want total rows to be shown