How to change the functionallity of button as well as text of it

I made some changes in my code but their is only one problem in it

I have a menu where i have two pages under user management tab.

1. create user

2. search user

i make some change in my code but their is one think that pamper me is when i click on edit link it redirect me to createuser page where submit button convert into update button with function.

Now when i click on create user page under user Management tab it show me update button so i cant create new user beacuse if btnsubmit.text=="Update" then it will execute update query.

Here is my code:

protected void btnSubmit_Click(object sender, EventArgs e)
{
if (btnSubmit.Text == "Submit")
{
this.Submit();
}
else if (btnSubmit.Text == "Update")
{
this.Update();
}
}

private void Submit()
{
con.Open();
da = new SqlDataAdapter();
dt = new DataTable();

string strSQL = "SELECT * FROM NewUser WHERE UserName = '" + tbName.Text + "'";

da.SelectCommand = new SqlCommand(strSQL, con);
da.Fill(dt);

if (dt.Rows.Count > 0) // Means first name is already present
{
lblmsg.Text = "This user is already added!";
}
else if (dt.Rows.Count == 0)
{
lblmsg.Visible = false;
string username = tbName.Text;
string pwd = tbPassword.Text;
string Confirmpwd = tbConfirmPassword.Text;
string Email = tbEmailID.Text;
string department = ddlDepartment.SelectedValue;
using (SqlCommand cmd = con.CreateCommand())
{
cmd.CommandText = "Insert into NewUser(UserName,Password,ConfirmPassword,EmailID,DepartmentName)values('" + tbName.Text + "','" + tbPassword.Text + "','" + tbConfirmPassword.Text + "','" + tbEmailID.Text + "','" + ddlDepartment.SelectedValue + "')";
cmd.Parameters.AddWithValue("@FirstName", tbName.Text.Trim());
cmd.Parameters.AddWithValue("@LastName", tbPassword.Text.Trim());
cmd.Parameters.AddWithValue("@DomainID", tbConfirmPassword.Text.Trim());
cmd.Parameters.AddWithValue("@EmailID", tbEmailID.Text.Trim());
cmd.Parameters.AddWithValue(@"RoleType", ddlDepartment.SelectedValue);
cmd.ExecuteNonQuery();
}
con.Close();
tbName.Text = "";
tbPassword.Text = "";
tbConfirmPassword.Text = "";
tbEmailID.Text = "";
tbName.Focus();
}
}
private void Update()
{
SqlCommand cmd;
String query;
con.Open();
query = "update NewUser set UserName='" + tbName.Text + "',Password='" + tbPassword.Text + "',ConfirmPassword='" + tbConfirmPassword.Text + "',EmailID='" + tbEmailID.Text + "',DepartmentName='" + ddlDepartment.SelectedValue + "' where ID=" + tbid.Text + "";
cmd = new SqlCommand(query, con);
cmd.CommandType = CommandType.Text;
cmd.ExecuteNonQuery();
con.Close();
Response.Redirect("~/SearchUser.aspx", false);
}
}
public string ButtonTextValue
{
get
{
if (Session["ButtonValue"] == null)
Session["ButtonValue"] = "Submit";

return Convert.ToString(Session["ButtonValue"]);
}
set
{
Session["ButtonValue"] = "Submit";
}
}

and on page load

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
btnSubmit.Text = ButtonTextValue;
}
}

and on search user page rowcommand of gridview has:

if (e.CommandName == "cmdBind")
{
LinkButton lb = (LinkButton)e.CommandSource;
Session["ButtonValue"] = "Update";
Response.Redirect("CreateUser.aspx?ID=" + lb.Text + "");
}