title: How can I define a IDataErrorInfo Error Property for multiple BO properties
body: <p>I'm starting to implement validation in my WPF project via the IDataErrorInfo interface.
  My business object contains multiple properties with validation info.  How do I get a list of ALL the error messages associated with the object.  My thought is that thats what the Error property is for, but I cannot track down anyone using this for reporting on multiple properties.  </p>
  
  <p>Thanks!</p>
  
  <pre><code>public string this[string property]
      {
          get {
  
              string msg = null;
              switch (property)
              {
                  case "LastName":
                      if (string.IsNullOrEmpty(LastName))
                          msg = "Need a last name";
                      break;
                  case "FirstName":
                      if (string.IsNullOrEmpty(LastName))
                          msg = "Need a first name";
                      break;
  
                  default:
                      throw new ArgumentException(
                          "Unrecognized property: " + property);
              }
              return msg;
  
          }
      }
  
      public string Error
      {
          get
          {
              return null ;
          }
      }
  </code></pre>