Error on moving to next page index on GridView with Alphabetical paging

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C#

ASP.NET

.NET

Hi,
I was able to get alphabetical paging in a Gridview. Problem - when I click the page 2(or 3 or 4 etc) for records whose records are more than the page size of 10, the alphabetic sorting is changed . I guess this is cause of the code in the page index changing event.Maybe I would need to change the "Constr" for the next 10 records of the selected Alphabet. Please help

protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
  {
     GridView1.PageIndex = e.NewPageIndex;
       
     constr = Select FirstName,MiddleName,LastName,Suffix from Offnames;
     binddata(constr);
  }

where the binddata is

public void binddata(string s)
  {
     SqlDataAdapter da = new SqlDataAdapter(constr, con);
     DataSet ds = new DataSet();
     da.Fill(ds);
     GridView1.DataSource = ds;
     GridView1.DataBind();
  }