get values of a datagridview selected row when button click on next form textboxes

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if (!IsPostBack)
{
DataTable dt1 = null;
DataRow[] dr = null;
DataTable dt2 = null;
DataRow[] dr2 = null;

try
{
FillCountry();

JavaScriptCalls();

if (HttpContext.Current.Request.QueryString.HasKeys())
{
btnSubmit.Text = "Update";
hdnId.Value = Request.QueryString[0].ToString();
SqlParameter objParam = new SqlParameter("@ID", hdnId.Value);
DataTable dt = SqlHelper.ExecuteDataset(strConn, CommandType.StoredProcedure, "LoginDetails_Get", objParam).Tables[0];
txtFirstName.Text = dt.Rows[0][1].ToString();
txtLastName.Text = dt.Rows[0][2].ToString();
txtAddress1.Text = dt.Rows[0][3].ToString();
txtAddress2.Text = dt.Rows[0][4].ToString();
txtCity.Text = dt.Rows[0][5].ToString();
string strCountry = dt.Rows[0][7].ToString();
dt1 = (DataTable)ViewState["Country"];
dr = dt1.Select("CountryName='" + strCountry + "'");
ddlCountry.SelectedValue = dr[0][0].ToString();
ViewState["Country"] = null;
if (dt.Rows[0][7].ToString() == "India")
{
ddlState.Style.Add("display", "block");
FillStateDropDown();
string strState = dt.Rows[0][6].ToString();
dt2 = (DataTable)ViewState["State"];
dr2 = dt2.Select("StateName='" + strState + "'");
ddlState.SelectedValue = dr2[0][0].ToString();
ViewState["State"] = null;
txtState.Style.Add("display", "none");
}
else
{
ddlState.Style.Add("display", "none");
txtState.Text = dt.Rows[0][6].ToString();
txtState.Style.Add("display", "block");
}
txtZip.Text = dt.Rows[0][8].ToString();
txtEmail.Text = dt.Rows[0][9].ToString();
//txtPassword.Attributes.Add("value", dt.Rows[0][10].ToString());
//txtConfirmPassword.Attributes.Add("value", dt.Rows[0][10].ToString());
hdnPwd1.Value = dt.Rows[0][10].ToString();
}
}
catch (Exception ex)
{
lblStatus.Text = ex.Message;
}
}

I used Query string to send Id of the record selected for edit and populated data using that id..(retrieved record matching that Id from db.)
query string..
try
{
if (e.CommandName == "DeleteItem")
{
lblStatus.Text = DeleteRecord(strConn, Convert.ToInt16(e.CommandArgument), "LoginDetails_Delete");
grdView.DataSource = EmployeeDetails();
grdView.DataBind();
}
if (e.CommandName == "EditItem")
{
Response.Redirect("AddEmployee.aspx?IdValue=" + Convert.ToInt32(e.CommandArgument));
}

.aspx page

<asp:TemplateField HeaderText="Edit" ItemStyle-Width="2%" ItemStyle-HorizontalAlign="Center">
<itemtemplate>
<asp:ImageButton ID="ImageButton1" runat="server" CommandName='EditItem' CommandArgument='<%# Eval("ID") %>'
ImageUrl="Edit.gif" />


<asp:TemplateField HeaderText="Delete" ItemStyle-Width="2%" ItemStyle-HorizontalAlign="Center">
<itemtemplate>
<asp:ImageButton ID="ImageButton2" runat="server" CommandName='Del