A Simpler Way To Create A Designer For A Templated Control
When you make a control that has templates, you have to write a designer which enables the templates to be edited within the designer. And I’m not talking simple code here. It’s like a couple hundred lines. When I look at the code required to make the designer, it’s also almost completely the same except for a few control-specific things.
So to make things a little easier, I wrote a SimpleTemplatedControlDesigner, which derives from TemplatedControlDesigner. This class lets you get going very quickly for a simple design experience on a templated control. For most cases, you don’t even need to extend it at all. And at the very least, you can use it to see how to write a templated control designer.
using System;
using System.Collections;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Diagnostics;
using System.Web.UI;
using System.Web.UI.Design;
using System.Web.UI.WebControls;
using System.Reflection;
namespace WebControlLibrary1 {
public class SimpleTemplatedControlDesigner : TemplatedControlDesigner {
// Override this if you want to be able to render the control when not all the templates have been defined.
protected virtual Boolean CanRenderWithTemplateEmpty( String templateName ) {
return false;
}
public override bool AllowResize {
get {
return !this.TemplatesAreEmpty || this.InTemplateMode;
}
}
#region Design-time HTML
public override string GetDesignTimeHtml() {
if ( !CanRenderWithCurrentTemplates() ) {
return this.GetEmptyDesignTimeHtml();
}
String designTimeHtml = String.Empty;
try {
((Control)this.Component).DataBind();
designTimeHtml = base.GetDesignTimeHtml();
} catch( Exception ex ) {
designTimeHtml = this.GetErrorDesignTimeHtml( ex );
}
return designTimeHtml;
}
protected override string GetEmptyDesignTimeHtml() {
return this.CreatePlaceHolderDesignTimeHtml( this.EditTemplateInstructions );
}
protected override string GetErrorDesignTimeHtml(Exception e) {
return this.CreatePlaceHolderDesignTimeHtml( "There was an error rendering the control." );
}
#endregion
#region Template-editing
private TemplateEditingVerb[] _templateEditingVerbs;
private String[] templateNames;
private Boolean TemplatesAreEmpty {
get {
foreach( String templateName in this.TemplateNames ) {
if ( GetTemplate( templateName ) == null ) {
return false;
}
}
return true;
}
}
private Boolean CanRenderWithCurrentTemplates() {
foreach( String templateName in this.TemplateNames ) {
if ( GetTemplate( templateName ) == null ) {
return this.CanRenderWithTemplateEmpty( templateName );
}
}
return true;
}
private Boolean TemplateIsEmpty( String templateName ) {
return GetTemplate( templateName ) == null;
}
protected virtual String EditTemplateInstructions {
get {
return "Right click to edit the templates for this control";
}
}
private String[] TemplateNames {
get {
if ( templateNames == null ) {
ArrayList names = new ArrayList();
Type componentType = this.Component.GetType();
foreach( PropertyInfo prop in componentType.GetProperties() ) {
if ( prop.PropertyType.IsAssignableFrom( typeof ( ITemplate ) ) ) {
names.Add( prop.Name );
}
}
if ( names.Count > 0 ) {
this.templateNames = new String[ names.Count ];
names.CopyTo( this.templateNames );
}
}
return templateNames;
}
}
private ITemplate GetTemplate( String templateName ) {
Type componentType = this.Component.GetType();
PropertyInfo property = componentType.GetProperty( templateName );
ITemplate value = property.GetValue( this.Component, null ) as ITemplate;
return value;
}
private void SetTemplate( String templateName, ITemplate template ) {
Type componentType = this.Component.GetType();
PropertyInfo property = componentType.GetProperty( templateName );
property.SetValue( this.Component, template, null );
}
protected override TemplateEditingVerb[] GetCachedTemplateEditingVerbs() {
if ( _templateEditingVerbs == null ) {
_templateEditingVerbs = new TemplateEditingVerb[ this.TemplateNames.Length ];
for( Int32 i = 0; i < _templateEditingVerbs.Length; i++ ) {
_templateEditingVerbs[ i ] = new TemplateEditingVerb( this.TemplateNames[ i ], i, this );
}
}
return _templateEditingVerbs;
}
protected override ITemplateEditingFrame CreateTemplateEditingFrame(TemplateEditingVerb verb) {
ITemplateEditingFrame frame = null;
if ( ( _templateEditingVerbs != null ) ) {
for ( Int32 i = 0; i < _templateEditingVerbs.Length; i++ ) {
if ( _templateEditingVerbs[ i ] == verb ) {
ITemplateEditingService teService = (ITemplateEditingService)GetService( typeof( ITemplateEditingService ) );
if ( teService != null ) {
frame = teService.CreateFrame( this, verb.Text, new String[] { this.TemplateNames[ i ] } );
}
}
}
}
return frame;
}
public override string GetTemplateContent(ITemplateEditingFrame editingFrame, string templateName, out bool allowEditing) {
String content = "";
allowEditing = true;
if ( ( _templateEditingVerbs != null ) ) {
for ( Int32 i = 0; i < _templateEditingVerbs.Length; i++ ) {
if ( _templateEditingVerbs[ i ] == editingFrame.Verb ) {
ITemplate editedTemplate = this.GetTemplate( templateName );
if ( editedTemplate != null ) {
content = this.GetTextFromTemplate( editedTemplate );
}
}
}
}
return content;
}
public override void SetTemplateContent(ITemplateEditingFrame editingFrame, string templateName, string templateContent) {
if ( ( _templateEditingVerbs != null ) ) {
for ( Int32 i = 0; i < _templateEditingVerbs.Length; i++ ) {
if ( _templateEditingVerbs[ i ] == editingFrame.Verb ) {
ITemplate newTemplate = null;
if ( templateContent != null && templateContent.Length != 0 ) {
newTemplate = this.GetTemplateFromText( templateContent );
}
this.SetTemplate( templateName, newTemplate );
}
}
}
}
#endregion
#region Dispose
private void DisposeTemplateEditingVerbs() {
if ( _templateEditingVerbs != null ) {
for( Int32 i = 0; i < _templateEditingVerbs.Length; i++ ) {
_templateEditingVerbs[ i ].Dispose();
}
_templateEditingVerbs = null;
}
}
protected override void Dispose(bool disposing) {
if ( disposing ) {
DisposeTemplateEditingVerbs();
}
base.Dispose( disposing );
}
public override void OnComponentChanged(object sender, ComponentChangedEventArgs ce) {
base.OnComponentChanged (sender, ce);
if ( ce.Member != null ) {
String name = ce.Member.Name;
if ( name == "Font" || name == "ForeColor" || name == "BackColor" ) {
DisposeTemplateEditingVerbs();
}
}
}
#endregion
}
}I know that's a whole heck of a lot of code... without a whole heck of a lot of comments... but you'll probably only really need to extend it at the CanRenderWithTemplateEmpty method. If nothing else, I hope this saves somebody some time.