Problem with the validation controls of asp.net

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C#

ASP.NET

i put validations controls in my webpage..

so that when i click Add Product button . I can show Errors in Validation summary..

but the problem is that if on the page i click on any other link or button to go to some other page.. it will force me to write on the textboxes which i validate..

i want them to work only for add product button.. not for the other links i click.
how can i do it.. here is the code.

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
    <style type="text/css">
    .style4
    {
        width: 100%;
    }
</style>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <p>
        Add new Products:</p>
<uc1:nav ID="nav1"  runat="server" />
<p align="center">
         </p>
<p align="center">
        <asp:Label ID="UploadStatusLabel" runat="server"></asp:Label>
</p>
<table class="style4">
    <tr>
        <td>
            Category Name:</td>
        <td>
        <asp:DropDownList ID="DropDownList1" runat="server" Height="20px" Width="170px">
        </asp:DropDownList>
        </td>
    </tr>
    <tr>
        <td>
            Product Name:</td>
        <td>
        <asp:TextBox ID="txtproname" runat="server" Width="174px"></asp:TextBox>
        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txtproname" 
            ErrorMessage="Please Enter Product Name" Display="Dynamic">*</asp:RequiredFieldValidator>
        
        </td>
    </tr>
    <tr>
        <td>
            Product Image:</td>
        <td>
        <asp:FileUpload ID="FileUpload1" runat="server" Width="218px" />
        </td>
    </tr>
    <tr>
        <td>
            Product Price:</td>
        <td>
        <asp:TextBox ID="txtproprice" runat="server" Width="138px"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>
            Description :</td>
        <td>
        <asp:TextBox ID="txtprodesc" runat="server" Height="50px" Width="267px" 
            TextMode="MultiLine"></asp:TextBox>
            <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="txtprodesc" 
            ErrorMessage="Enter Product Description" Display="Dynamic">*</asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td>
            Original Price</td>
        <td>
            <asp:TextBox ID="txtOrigional" runat="server" Width="136px"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>
            Stock Quantity</td>
        <td>
            <asp:DropDownList ID="dpquantity" runat="server">
                <asp:ListItem>0</asp:ListItem>
                <asp:ListItem>10</asp:ListItem>
                <asp:ListItem>20</asp:ListItem>
                <asp:ListItem>50</asp:ListItem>
                <asp:ListItem>100</asp:ListItem>
            </asp:DropDownList>
        </td>
    </tr>
    <tr>
        <td colspan="2">
<p align="center">
         <asp:Button ID="btnaddproduct" runat="server" onclick="btnaddproduct_Click" 
            Text="Add Product" Width="115px" />
    
        </p>
        </td>
    </tr>
    <tr>
        <td align="center" colspan="2">
            <asp:ValidationSummary ID="ValidationSummary1" runat="server" />
        </td>
    </tr>
</table>
    <p align="center">
        <asp:Label ID="lblresult" runat="server"></asp:Label>
    </p>
    <p align="center">
         </p>
    <p align="center">
        <asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
            AutoGenerateColumns="False" onrowcancelingedit="_rowcancel" 
            onrowdeleting="_rowdeleting" onrowediting="_rowediting" 
            onrowupdating="_rowupdating" Width="446px" 
            onpageindexchanging="_pagechange" HorizontalAlign="Center" 
            onselectedindexchanged="GridView1_SelectedIndexChanged">
            <Columns>
                <asp:TemplateField HeaderText="ProductID">
                    <EditItemTemplate>
                        <asp:TextBox ID="txtproid" runat="server" Text='<%# Eval("ProductID") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="lblproid" runat="server" Text='<%# Eval("ProductID") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="ProductName">
                    <EditItemTemplate>
                        <asp:TextBox ID="txtproname" runat="server" Text='<%# Eval("ProductName") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="lblproname" runat="server" Text='<%# Eval("ProductName") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="UnitCost">
                    <EditItemTemplate>
                        <asp:TextBox ID="txtproprice" runat="server" Text='<%# Eval("UnitCost") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="lblproprice" runat="server" Text='<%# Eval("UnitCost") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:CommandField ShowEditButton="True" />
                <asp:CommandField ShowDeleteButton="True" />
            </Columns>
        </asp:GridView>
    </p>
    <p align="center">
         </p>
    <p align="center">
         </p>
    <p>
         </p>
    <p>
         </p>
    <p>
         </p>
</asp:Content>