source: branches/HeuristicLab.Hive.Azure/HeuristicLab.Clients.Hive.CloudManager/3.3/Validation.cs @ 15917

using System;
using System.ComponentModel;
using System.Reflection;
using System.Windows.Forms;

namespace HeuristicLab.Clients.Hive.CloudManager {
  // for more info see: http://stackoverflow.com/questions/769184/winform-ui-validation
  public class Validation {
    public static bool hasValidationErrors(System.Windows.Forms.Control.ControlCollection controls) {
      bool hasError = false;

      // Now we need to loop through the controls and deterime if any of them have errors
      foreach (Control control in controls) {
        // check the control and see what it returns
        bool validControl = IsValid(control);
        // If it's not valid then set the flag and keep going.  We want to get through all
        // the validators so they will display on the screen if errorProviders were used.
        if (!validControl)
          hasError = true;

        // If its a container control then it may have children that need to be checked
        if (control.HasChildren) {
          if (hasValidationErrors(control.Controls))
            hasError = true;
        }
      }
      return hasError;
    }

    // Here, let's determine if the control has a validating method attached to it
    // and if it does, let's execute it and return the result
    private static bool IsValid(object eventSource) {
      string name = "EventValidating";

      Type targetType = eventSource.GetType();

      do {
        FieldInfo[] fields = targetType.GetFields(
             BindingFlags.Static |
             BindingFlags.Instance |
             BindingFlags.NonPublic);

        foreach (FieldInfo field in fields) {
          if (field.Name == name) {
            EventHandlerList eventHandlers = ((EventHandlerList)(eventSource.GetType().GetProperty("Events",
                (BindingFlags.FlattenHierarchy |
                (BindingFlags.NonPublic | BindingFlags.Instance))).GetValue(eventSource, null)));

            Delegate d = eventHandlers[field.GetValue(eventSource)];

            if ((!(d == null))) {
              Delegate[] subscribers = d.GetInvocationList();

              // ok we found the validation event,  let's get the event method and call it
              foreach (Delegate d1 in subscribers) {
                // create the parameters
                object sender = eventSource;
                CancelEventArgs eventArgs = new CancelEventArgs();
                eventArgs.Cancel = false;
                object[] parameters = new object[2];
                parameters[0] = sender;
                parameters[1] = eventArgs;
                // call the method
                d1.DynamicInvoke(parameters);
                // if the validation failed we need to return that failure
                if (eventArgs.Cancel)
                  return false;
                else
                  return true;
              }
            }
          }
        }

        targetType = targetType.BaseType;

      } while (targetType != null);

      return true;
    }

  }
}