WinForm UI Validation

1) Just copy and paste this section of code to your project. We're using Reflection so you need to add System.Refelection to your using statements

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 controlin 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 boolIsValid(object eventSource) 
    { 
        string name ="EventValidating"; 
 
        Type targetType = eventSource.GetType(); 
 
        do 
        { 
            FieldInfo[] fields= targetType.GetFields( 
                 BindingFlags.Static| 
                 BindingFlags.Instance| 
                 BindingFlags.NonPublic); 
 
            foreach (FieldInfo fieldin 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 d1in subscribers) 
                        { 
                            // create the parameters 
                            object sender= eventSource; 
                            CancelEventArgs eventArgs= newCancelEventArgs(); 
                            eventArgs.Cancel= false; 
                            object[] parameters= newobject[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) 
                                returnfalse; 
                            else 
                                returntrue; 
                        } 
                    } 
                } 
            } 
 
            targetType = targetType.BaseType; 
 
        } while(targetType !=null); 
 
        return true; 
    } 
 
} 

2) Use the standard Validating event on any control you want to validate. Be Sure to use e.Cancel when the validation fails!

private void txtLastName_Validating(object sender, CancelEventArgs e)     {         if (txtLastName.Text.Trim() == String.Empty)         {             errorProvider1.SetError(txtLastName, "Last Name is Required");             e.Cancel = true;         }         else             errorProvider1.SetError(txtLastName, "");     } 

3) Don't skip this step! Set the AutoValidate property on the form toEnableAllowFocusChange. This will allow tabbing to another control even when the validation fails.

4) Finally, in your Submit Button method, call the Validation method and specify what container you want to check. It can be the whole form, or just a container on the form like a Panel or a Group.

private void btnSubmit_Click(object sender, EventArgs e)     {         // the controls collection can be the whole form or just a panel or group         if (Validation.hasValidationErrors(frmMain.Controls))             return;          // if we get here the validation passed         this.close();     } http://stackoverflow.com/questions/769184/winform-ui-validation