title: Regex for semicolon separated numbers string in ConfigurationSectionDesigner validation?
body: <p>Need to apply Regex validation for a string with semicolon separated HTTP status codes:</p>
  
  <pre><code>"202;500;503"
  </code></pre>
  
  <p>I tried this regex</p>
  
  <pre><code>^([0-9]+;)*[0-9]+$
  </code></pre>
  
  <p>but i get an exception:</p>
  
  <p>The value for the property 'retryStatusCodes' is not valid. The error is: The value does not conform to the validation regex string <code>^([0-9]+;)*[0-9]+$</code>.</p>
  
  <p>How is that possible? I tested it here: <a href="https://regexr.com/" rel="nofollow noreferrer">https://regexr.com/</a></p>
  
  <p>and it worked</p>
  
  <p>Why it doesnt work in C# code?</p>
  
  <p>I use it for validation of attrtibutes in ConfigurationSectionDesigner, auto-generated code for this attribute:</p>
  
  <pre><code>    /// &lt;summary&gt;
      /// Gets or sets the RetryStatusCodes.
      /// &lt;/summary&gt;
      [global::System.CodeDom.Compiler.GeneratedCodeAttribute("ConfigurationSectionDesigner.CsdFileGenerator", "2.0.3.2")]
      [global::System.ComponentModel.DescriptionAttribute("The RetryStatusCodes.")]
      [global::System.Configuration.RegexStringValidatorAttribute("^([0-9]+;)*[0-9]+$")]
      [global::System.Configuration.ConfigurationPropertyAttribute(global::XXX.XXX.XXX.RetryStatusCodesPropertyName, IsRequired=true, IsKey=false, IsDefaultCollection=false)]
      public virtual string RetryStatusCodes
      {
          get
          {
              return ((string)(base[global::XXX.XXX.XXX.RetryStatusCodesPropertyName]));
          }
          set
          {
              base[global::XXX.XXX.XXX.RetryStatusCodesPropertyName] = value;
          }
      }
  </code></pre>