Question

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.

Thanks!

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 ;
        }
    }

Answer 1

Yeah, I see where you could use the indexer. Not a bad way to go I guess. I was really focused on the ‘Error’ property though. I like the notion of having the errors contained within the business object. I think what I want to do doesnt exist natively, so I just created a dictionary of errors (updated anytime a property changes) on the object and let the Error return a CarriageReturn delimited list of errors, like so :

    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(FirstName))
                        msg = "Need a first name";
                    break;
                default:
                    throw new ArgumentException(
                        "Unrecognized property: " + property);
            }

            if (msg != null && !errorCollection.ContainsKey(property))
                errorCollection.Add(property, msg);
            if (msg == null && errorCollection.ContainsKey(property))
                errorCollection.Remove(property);

            return msg;
        }
    }

    public string Error
    {
        get
        {
            if(errorCollection.Count == 0)
                return null;

            StringBuilder errorList = new StringBuilder();
            var errorMessages = errorCollection.Values.GetEnumerator();
            while (errorMessages.MoveNext())
                errorList.AppendLine(errorMessages.Current);

            return errorList.ToString();
        }
    }