.NET Blog - Chris Frazier Style

I had been using the treeview from the IEWebControls library - which is great for IE, but just doesn't look or act so hot in anything else. So I wanted to find a TreeView control that would act as a SiteMap, and the squishyTREE control by squishyware fit the bill; almost perfectly. What the control lacked was a simple addition that would allow the use of hyperlinks without a postback.

Enter NavigateUrl.

The modifications I made were only in a few files:

• TreeNode.cs
• StandardRenderingAgent.cs
• TreeView.cs

I suppose this could go for the other RenderingAgents included with the control, but this is what I needed. You can see a live version here.

The code that supports the NavigateUrl property has to be in the TreeNode class, because that is what we will be clicking for navigation. The code:

public string NavigateUrl{ get{ 
 object savedState = ViewState["NavigateUrl"]; 
 if(savedState != null){ 
 return savedState.ToString(); 
 } 
 
 return string.Empty; 
 } 
 set{ ViewState["NavigateUrl"] = value; } }

Pretty simple so far. This code is just the standard server control property goop.

The container of the TreeNode, TreeView,  had to be modified in a few places to allow using a url instead of simply a postback reference. Basically, I added support for anchor urls into the existing TreeView, modifying the overloaded methods where needed. Here are the places that were changed in TreeView.cs:

public void XmlBind(System.Xml.XmlDocument doc, 
 string urlAttribute, 
 string textAttribute, 
 string keyAttribute, 
 string checkAttribute, 
 string checkDefaultsAttribute){









    foreach(XmlNode node in doc.DocumentElement.ChildNodes){ 
       this.addChildNode(node, 
                         urlAttribute, 
                         textAttribute, 
                         keyAttribute, 
                         checkAttribute, 
                         checkDefaultsAttribute); 
     }
}

public void XmlBind(System.Xml.XmlDocument doc, 
                    string urlAttribute, 
                    string textAttribute, 
                    string keyAttribute){ 
      this.XmlBind(doc, urlAttribute, textAttribute, keyAttribute, "", ""); 
}

private void addChildNode(XmlNode node, 
                          string urlAttribute, 
                          string textAttribute, 
                          string keyAttribute, 
                          string checkAttribute,
                          string checkDefaultsAttribute){
    this.addChildNode(node, 
                      urlAttribute, 
                      textAttribute, 
                      keyAttribute, 
                      null, 
                      checkAttribute, 
                      checkDefaultsAttribute); 
}

private void addChildNode(XmlNode node, 
                          string urlAttribute,
                          string textAttribute, 
                          string keyAttribute,
                          TreeNode tNode, 
                          string checkAttribute, 
                          string checkDefaultsAttribute){
   string url = string.Empty; 
   string text; 
   string key = ""; 
   bool checkbox = false; 
   bool isChecked = false; 
 
   if(node.Attributes[urlAttribute] != null){
      url = node.Attributes[urlAttribute].Value; 
   } 
 
   text = node.Attributes[textAttribute].Value; 
 
   if(node.Attributes[keyAttribute] != null){ 
      key = node.Attributes[keyAttribute].Value; 
   } 
   if(node.Attributes[checkAttribute] != null){ 
      checkbox = Convert.ToBoolean(node.Attributes[checkAttribute].Value); 
   } 
   if(node.Attributes[checkDefaultsAttribute] != null){ 
      isChecked = Convert.ToBoolean(node.Attributes[checkDefaultsAttribute].Value); 
   } 
 
   TreeNode n; 
   
   if(tNode == null){//add to the TreeView
      n = this.AddNode(text, key, checkbox); 
      n.NavigateUrl = url; 
   }else{//add to the TreeNode 
      n = tNode.AddNode(text, key, checkbox); 
      n.NavigateUrl = url; 
   }

 ...
    foreach(XmlNode child in node.ChildNodes){ 
      if(child.Name != "taggedValue"){ 
         this.addChildNode(child, 
                           urlAttribute, 
                           textAttribute, 

                           keyAttribute, 

                           n, 
                           checkAttribute, 
                           checkDefaultsAttribute); 
      }
    }

protected override void LoadViewState(object savedState){  
//load the treeview back from XML 
    if(savedState != null){ 
       string xml = savedState.ToString(); 
       XmlDocument doc = new XmlDocument(); 
       doc.LoadXml(xml); 
       //xmlbind 
       this.XmlBind(doc, 
                    TreeView.urlAttribute, 
                    TreeView.textAttribute, 
                    TreeView.keyAttribute, 
                    TreeView.showChkAttribute, 
                    TreeView.chkAttribute);

    }

}







internal const string textAttribute = "t";
internal const string keyAttribute = "k"; 
internal const string chkAttribute = "c";
internal const string showChkAttribute = "s"; 
internal const string urlAttribute = "u"; //added this attribute

The code that was changed in StandardRenderingAgent was in the RenderNodeText(TreeNode node, HtmlTextWriter output) method:

if(!useLink) {
 //name the anchor, in case you need to jump 
 output.Write("<a name='" + node.Key + "'> </a>"); 
 output.WriteBeginTag("a"); 
 if(node.NavigateUrl == string.Empty) 
    output.WriteAttribute("href", 
      this.TreeView.Page.GetPostBackClientHyperlink(this.TreeView, node.UniqueID), 
      false); 
 else 
    output.WriteAttribute("href", node.NavigateUrl, false);
    output.WriteAttribute("class", this.TreeView.CssClass); 
    output.Write(HtmlTextWriter.TagRightChar); }

That's pretty much it. I think it was rather straightforward, plus the hard work was already done for me. Now I've got a simple SiteMap that will navigate to pages I specify at any time without postbacks.