/// <summary>
/// Adds the error message for the property to the error dictionary.
/// </summary>
/// <param name="propertyName">The name of the property.</param>
/// <param name="errorMessage">The error message.</param>
private void AddError(string propertyName, string errorMessage)
{
_validationErrors[propertyName] = errorMessage;
_xmlDependencyViewModel.SetValid(IsValid);
}
