Verify the use of controls 7 (validationsummary)

 1 <p>First name 
 2    <asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox>
 3     &nbsp;
 4    <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
 5     Runat="server" ErrorMessage="You must enter your first name" 
 6     ControlToValidate="TextBox1"></asp:RequiredFieldValidator>
 7  </p>
 8  <p>Last name 
 9    <asp:TextBox ID="TextBox2" Runat="server"></asp:TextBox>
10     &nbsp;
11    <asp:RequiredFieldValidator ID="RequiredFieldValidator2" 
12     Runat="server" ErrorMessage="You must enter your last name" 
13     ControlToValidate="TextBox2"></asp:RequiredFieldValidator>
14 </p>
15 <p>
16    <asp:Button ID="Button1" OnClick="Button1_Click" Runat="server" 
17     Text="Submit"></asp:Button>
18 </p>
19 <p>
20    <asp:ValidationSummary ID="ValidationSummary1" Runat="server" 
21     HeaderText="You received the following errors:">
22    </asp:ValidationSummary>
23 </p>
24 <p>
25    <asp:Label ID="Label1" Runat="server"></asp:Label>
26 </p>

1 <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
2  Runat="server" ErrorMessage="You must enter your first name" Text="*"
3  ControlToValidate="TextBox1"></asp:RequiredFieldValidator>
4  
5 or
6 
7 <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
8  Runat="server" ErrorMessage="You must enter your first name"
9  ControlToValidate="TextBox1">*</asp:RequiredFieldValidator>

In this way, there will be no repeated display