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Overview

The OnlyOffice Control for ASP.NET provides a simple way to integrate document editing capabilities into your web applications. This guide covers the fundamental steps to get started.

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Registering the Control

First, register the OnlyOffice control in your ASPX page: 
<%@ Register Src="~/Controls/OnlyOfficeEditor/OnlyOfficeEditor.ascx" 
    TagPrefix="oo" 
    TagName="Editor" %>
Then add the control to your page markup: 
<oo:Editor ID="docEditor" runat="server" />

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Essential Properties

Configure the control by setting these key properties in your code-behind:
1
Configure OnlyOffice Server URL
2
Set the URL to your OnlyOffice Document Server API:
3
docEditor.OnlyOfficeApiUrl = "https://your-server.com/web-apps/apps/api/documents/api.js";
4
Set JWT Secret
5
Provide the JWT secret that matches your OnlyOffice server configuration:
6
docEditor.JwtSecret = "your_jwt_secret_key";
7
The JWT secret must match exactly with the secret configured on your OnlyOffice Document Server. Mismatched secrets will cause authentication failures.
8
Configure Public Base URL
9
Set the public URL where your application is accessible:
10
docEditor.PublicBaseUrl = "https://your-app.com";
11
This URL is used to generate callback and download URLs that the OnlyOffice server needs to access.

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Loading a Document

There are three primary methods to load documents into the editor:

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From Byte Array

Load a document from a byte array in memory: 
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        string sampleFilePath = Server.MapPath("~/doc.docx");
        if (File.Exists(sampleFilePath))
        {
            byte[] fileBytes = File.ReadAllBytes(sampleFilePath);
            docEditor.SetDocumentFromBytes(fileBytes, "doc.docx");
        }
    }
}

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From File Upload

Load a document from a FileUpload control: 
protected void btnUpload_Click(object sender, EventArgs e)
{
    if (!fuFile.HasFile)
        return;
    
    docEditor.SetDocumentFromBytes(fuFile.FileBytes, fuFile.FileName);
}

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From Server File Path

Load a document directly from a file path on the server: 
string serverPath = Server.MapPath("~/Documents/report.docx");
docEditor.SetDocumentFromFile(serverPath, "Monthly Report.docx");

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Displaying the Editor

Once a document is loaded, the editor renders automatically. The control generates:
  • A container div for the editor (OnlyOfficeEditor.ascx.cs:66)
  • JavaScript initialization code
  • Configuration with JWT tokens
  • Event handlers for document callbacks

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Checking Document Status

You can verify if a document is loaded: 
if (docEditor.HasDocument)
{
    // Document is loaded and ready
    litStatus.Text = "Document loaded: " + docEditor.DocumentName;
}

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Editor Modes

Set the editor mode based on your requirements: 
// Edit mode (default)
docEditor.Mode = "edit";

// View-only mode
docEditor.Mode = "view";

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Customizing Appearance

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Editor Height

Adjust the editor container height: 
docEditor.EditorHeight = "600px";

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Language

Set the editor interface language: 
docEditor.Lang = "es"; // Spanish
docEditor.Lang = "en"; // English

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User Configuration

Set user information that appears in the editor: 
docEditor.UserId = "123";
docEditor.UserDisplayName = "John Doe";
User information is important for collaboration features and document history tracking.

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Complete Example

Here’s a complete example integrating all the basics: 
using System;
using System.IO;
using System.Web.UI;

namespace YourApp
{
    public partial class DocumentEditor : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                // Configure OnlyOffice connection
                docEditor.OnlyOfficeApiUrl = "https://docserver.example.com/web-apps/apps/api/documents/api.js";
                docEditor.JwtSecret = "your_secret_key";
                docEditor.PublicBaseUrl = "https://yourapp.example.com";
                
                // Set editor preferences
                docEditor.Mode = "edit";
                docEditor.Lang = "en";
                docEditor.EditorHeight = "650px";
                
                // Set user info
                docEditor.UserId = Session["UserId"]?.ToString() ?? "1";
                docEditor.UserDisplayName = Session["UserName"]?.ToString() ?? "Guest";
            }
        }
        
        protected void btnUpload_Click(object sender, EventArgs e)
        {
            if (!fuFile.HasFile)
            {
                lblMessage.Text = "Please select a file";
                return;
            }
            
            docEditor.SetDocumentFromBytes(fuFile.FileBytes, fuFile.FileName);
            lblMessage.Text = "Document loaded: " + fuFile.FileName;
        }
    }
}

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Next Steps

Document Upload

Learn advanced file upload and storage techniques

Advanced Configuration

Customize editor behavior and security settings

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