gridview paging is not working

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C#

C#4.0

i have one gridview of all employees with check box column.
when i check records, details of that employees comes in second grid view.
now, my first grid view paging works. but the second gridview paging do not work.
i have two problems.
1.when i check some records in first grid view and changes the page, the records displayed in the second gridview are only from current page. previous checks are refreshed. so how do i get those values in next gridview
2.in second grid view when i click to second page. the grid view disappears.

after adding a theme to gridview for paging i have added this code to first grid view

protected void gvDetails_PageIndexChanging1(object sender, GridViewPageEventArgs e)
{
    gvDetails.PageIndex = e.NewPageIndex;

    string str1 = "SELECT ID, FirstName, LastName FROM EmpMaster";
    Command = new SqlCommand(str1, con);
    Command.CommandType = CommandType.Text;
    SqlDataAdapter da = new SqlDataAdapter(Command);
    da.Fill(dtLogin);

    gvDetails.DataSource = dtLogin;
    gvDetails.DataBind();
}

and, this doesnt works for second one,

protected void gvDisplayRecords_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    gvDisplayRecords.PageIndex = e.NewPageIndex;
    gvDisplayRecords.DataSource = dtLogin;
    gvDisplayRecords.DataBind();
    gvDisplayRecords.Visible = true;
}

so please post the solution.......

[edit]Code block added, "Treat my content as plain text..." option disabled - OriginalGriff[/edit]