Adding content to an "Editable region" web part programmatically
        
      
      In some cases it’s necessary to add particular content to the Editable region programmatically. Our API can handle this query. Please read further to see such example code which can be used in your custom scripts.
      Basically, you will need to add content to editable region using 
EditableWebParts property of the 
PageInfo class. Then it's necessary to save 
DocumentContent value to particular node and call 
Update on that document's node. Please see following code for inspiration:
// Add content text to the editable region (EditableRegion is ID of appropriate Editable region within the template)        
CMS.CMSHelper.CMSContext.CurrentPageInfo.EditableWebParts["EditableRegion"] = "<div>content</div>";
// Node ID
int nodeid = CMS.CMSHelper.CMSContext.CurrentDocument.NodeID;
// Tree node
CMS.TreeEngine.TreeNode node = null;
// Tree provider
UserInfo ui = UserInfoProvider.GetUserInfo("administrator");
CMS.TreeEngine.TreeProvider tree = new CMS.TreeEngine.TreeProvider(ui);
// Get Single node specified by its ID
node = tree.SelectSingleNode(nodeid);
// Set DocumentContent value
node.SetValue("DocumentContent", CMS.CMSHelper.CMSContext.CurrentPageInfo.DocumentContent);
// Update node
node.Update();
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See also: Update document example in Developer’s Guide 
 Kentico CMS APIApplies to: Kentico CMS 5.x