How do I show total record no in a txtbox when button is clicked

<label class="col-sm-3">
                    Count:
                </label>
                <div class="col-sm-2">
                    <asp:TextBox runat="server" ID="txtCount" AutoPostBack="true"></asp:TextBox>
                    <asp:Button runat="server" ID="check" OnClick="check_Click" Text="Check"  />


                </div>

protected void check_Click(object sender, EventArgs e)
       {

               var employee = _service.GetAllEmployee();

               txtCount.Text = employee.Count().ToString();

       }