/// <summary>
/// Gets the error message, taken from the results of <see cref="Validation"/>, that arose due to the
/// value of the input <paramref name="propertyName"/>.
/// </summary>
/// <param name="propertyName">The name of the property to check for errors.</param>
/// <returns>A string representation of the error, or null if there isn't one.</returns>
string IDataErrorInfo.this[string propertyName]
{
get
{
if (_showValidationErrors && _validation != null)
{
var result = ValidationResult.Combine(_validation.GetResults(this, propertyName));
return(result.Success ? null : result.GetMessageString("\n"));
}
return(null);
}
}