title: regular expression allow only one specific special character and numbers in asp.net vb
body: <p>i want to get interest value from users through asp.net textbox. it accepts numbers and optional to enter "%" only. prohibit to enter any other special characters or any alphabet letters.  </p>
  
  <pre><code>                      &lt;div class="row"&gt;
                         &lt;div class="medium-6 columns"&gt;
                        Current Interest (APR) that you pay
                        &lt;asp:RegularExpressionValidator ID="rgv2" 
                                 ControlToValidate="txtCurrentInterest" runat="server" 
                                 ErrorMessage="Interest be in numbers" ValidationGroup="vgSubmit" 
                                 ValidationExpression=""&gt;*&lt;/asp:RegularExpressionValidator&gt;
  
                        &lt;asp:RequiredFieldValidator ID="rv6" runat="server" ControlToValidate="txtCurrentInterest" ErrorMessage="Current Interest is Required" ValidationGroup="vgSubmit"&gt;*&lt;/asp:RequiredFieldValidator&gt;
                          &lt;asp:TextBox ID="txtCurrentInterest" runat="server"&gt;&lt;/asp:TextBox&gt;
                         &lt;/div&gt;                    
                      &lt;/div&gt; 
  </code></pre>