Quick Start

Overview

This guide will walk you through creating a basic page that allows users to upload, edit, and download documents using the OnlyOffice Control.

Basic Implementation

First, register the OnlyOffice Control on your ASPX page:

Default.aspx

<%@ Page Language="C#" 
         AutoEventWireup="true" 
         CodeBehind="Default.aspx.cs" 
         Inherits="YourNamespace._Default" 
         ValidateRequest="false" %>
<%@ Register Src="~/Controls/OnlyOfficeEditor/OnlyOfficeEditor.ascx" 
             TagPrefix="oo" 
             TagName="Editor" %>

Set ValidateRequest="false" on pages using the OnlyOffice Control to prevent request validation issues with document content.

Add Control to Page

Add the editor control to your page markup:

Default.aspx

<!DOCTYPE html>
<html>
<head runat="server">
    <title>Document Editor</title>
    <style>
        iframe {
            height: 700px;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <div>
            <h1>OnlyOffice Document Editor</h1>
            
            <!-- File Upload Section -->
            <div>
                <asp:FileUpload ID="fuFile" runat="server" />
                <asp:Button ID="btnUpload" 
                            runat="server" 
                            Text="Upload and Open" 
                            OnClick="btnUpload_Click" />
                <asp:Literal ID="litStatus" runat="server" />
            </div>
            
            <!-- OnlyOffice Editor -->
            <oo:Editor ID="docEditor" 
                       runat="server" 
                       CaptureTriggerId="btnDownload" />
            
            <!-- Download Button -->
            <div>
                <asp:Button ID="btnDownload" 
                            runat="server" 
                            Text="Download Document" 
                            OnClick="btnDownload_Click" />
            </div>
        </div>
    </form>
</body>
</html>

Understanding CaptureTriggerId

The CaptureTriggerId property specifies which button(s) should trigger document capture from the editor. When clicked, the control automatically:

Requests the current document from the OnlyOffice editor
Stores it as base64 in a hidden field
Triggers a postback

You can specify multiple buttons separated by commas: CaptureTriggerId="btnSave,btnDownload,btnConvert"

Implement Upload Handler

In your code-behind file, implement the upload functionality:

Default.aspx.cs

using System;
using System.IO;
using System.Web.UI;

namespace YourNamespace
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                // Optional: Load a default document
                string sampleFilePath = Server.MapPath("~/Documents/sample.docx");
                if (File.Exists(sampleFilePath))
                {
                    docEditor.SetDocumentFromFile(sampleFilePath, "sample.docx");
                }
            }
        }

        protected void btnUpload_Click(object sender, EventArgs e)
        {
            if (!fuFile.HasFile)
            {
                litStatus.Text = "<span style='color:red;'>Please select a file</span>";
                return;
            }

            // Load the uploaded file into the editor
            docEditor.SetDocumentFromBytes(fuFile.FileBytes, fuFile.FileName);
            
            // Set editor mode (optional)
            docEditor.Mode = "edit"; // or "view" for read-only
            
            litStatus.Text = "<span style='color:green;'>Document loaded successfully</span>";
        }
    }
}

Implement Download Handler

Add functionality to download the edited document:

Default.aspx.cs

protected void btnDownload_Click(object sender, EventArgs e)
{
    // Get the edited document bytes
    byte[] documentBytes = docEditor.GetEditedDocumentBytes();

    if (documentBytes == null || documentBytes.Length == 0)
    {
        litStatus.Text = "<span style='color:red;'>No edited document available</span>";
        return;
    }

    // Clear the cached document
    docEditor.ClearEditedDocument();

    // Prepare file for download
    var fileName = docEditor.DocumentName ?? "document.docx";
    
    Response.Clear();
    Response.ContentType = "application/octet-stream";
    Response.AddHeader("Content-Disposition", "attachment; filename=" + fileName);
    Response.AddHeader("Content-Length", documentBytes.Length.ToString());
    Response.BinaryWrite(documentBytes);
    Response.End();
}

The CaptureTriggerId property automatically captures the document when the download button is clicked, so you don’t need to manually call capture methods.

Configuring Editor Properties

You can configure various properties of the OnlyOffice editor:

Basic Configuration

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        // Configure editor properties
        docEditor.Mode = "edit";              // "edit" or "view"
        docEditor.Lang = "en";                 // Language: "en", "es", "fr", etc.
        docEditor.EditorHeight = "600px";     // Editor height
        docEditor.UserId = "123";              // Current user ID
        docEditor.UserDisplayName = "John Doe"; // Current user name
        
        // Load a document
        LoadDocument();
    }
}

Loading Documents

There are three ways to load documents into the editor:

// Load from byte array (e.g., from upload)
byte[] fileBytes = fuFile.FileBytes;
string fileName = fuFile.FileName;
docEditor.SetDocumentFromBytes(fileBytes, fileName);

Advanced Features

PDF Conversion

Convert the current document to PDF:

protected void btnConvertToPdf_Click(object sender, EventArgs e)
{
    try
    {
        // Convert the current document to PDF bytes
        byte[] pdfBytes = docEditor.ConvertCurrentDocumentToPdfBytes();
        
        // Download the PDF
        Response.Clear();
        Response.ContentType = "application/pdf";
        Response.AddHeader("Content-Disposition", 
            "attachment; filename=" + Path.GetFileNameWithoutExtension(docEditor.DocumentName) + ".pdf");
        Response.BinaryWrite(pdfBytes);
        Response.End();
    }
    catch (Exception ex)
    {
        litStatus.Text = "<span style='color:red;'>Error converting to PDF: " + ex.Message + "</span>";
    }
}

PDF conversion requires the OnlyOffice Document Server conversion service to be available.

View-Only Mode

Set the editor to read-only mode:

protected void btnViewOnly_Click(object sender, EventArgs e)
{
    // Switch to view mode
    docEditor.Mode = "view";
    
    // Reload the page to apply the change
    Response.Redirect(Request.Url.ToString());
}

Checking Document Status

Check if a document is loaded or edited:

protected void Page_Load(object sender, EventArgs e)
{
    // Check if a document is currently loaded
    if (docEditor.HasDocument)
    {
        lblDocumentName.Text = docEditor.DocumentName;
    }
    
    // Check if there's an edited version
    if (docEditor.HasEditedDocument)
    {
        btnDownload.Enabled = true;
        btnDownload.Text = "Download Edited Document";
    }
}

Complete Example

Here’s a complete working example:

<%@ Page Language="C#" 
         AutoEventWireup="true" 
         CodeBehind="Default.aspx.cs" 
         Inherits="OnlyOfficeControl._Default" 
         ValidateRequest="false" %>
<%@ Register Src="~/Controls/OnlyOfficeEditor/OnlyOfficeEditor.ascx" 
             TagPrefix="oo" 
             TagName="Editor" %>

<!DOCTYPE html>
<html>
<head runat="server">
    <title>Document Editor</title>
    <style>
        iframe { height: 700px; }
        .toolbar { padding: 20px; background: #f5f5f5; margin-bottom: 20px; }
        .editor-container { padding: 20px; }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <div class="toolbar">
            <asp:FileUpload ID="fuFile" runat="server" />
            <asp:Button ID="btnUpload" 
                        runat="server" 
                        Text="Upload and Open" 
                        OnClick="btnUpload_Click" />
            <asp:Literal ID="litStatus" runat="server" />
        </div>
        
        <div class="editor-container">
            <oo:Editor ID="docEditor" 
                       runat="server" 
                       CaptureTriggerId="btnDownload" />
            
            <div style="margin-top: 20px;">
                <asp:Button ID="btnDownload" 
                            runat="server" 
                            Text="Save and Download" 
                            OnClick="btnDownload_Click" />
            </div>
        </div>
    </form>
</body>
</html>

Common Patterns

Upload, Edit, and Save Workflow

// 1. User uploads document
protected void btnUpload_Click(object sender, EventArgs e)
{
    docEditor.SetDocumentFromBytes(fuFile.FileBytes, fuFile.FileName);
    docEditor.Mode = "edit";
}

// 2. User edits in OnlyOffice
// (happens in browser)

// 3. User saves document
protected void btnSave_Click(object sender, EventArgs e)
{
    byte[] editedBytes = docEditor.GetEditedDocumentBytes();
    
    // Save to database, file system, etc.
    SaveToDatabase(editedBytes, docEditor.DocumentName);
    
    docEditor.ClearEditedDocument();
}

Load from Database

protected void LoadDocumentFromDatabase(int documentId)
{
    // Retrieve document from database
    var doc = GetDocumentFromDatabase(documentId);
    
    // Load into editor
    docEditor.SetDocumentFromBytes(doc.Content, doc.FileName);
    docEditor.Mode = "edit";
    docEditor.UserId = CurrentUser.Id.ToString();
    docEditor.UserDisplayName = CurrentUser.FullName;
}

Troubleshooting

Editor doesn't show document

Verify that:

A document was loaded using one of the SetDocument* methods
The HasDocument property returns true
No JavaScript errors in the browser console

Download returns empty document

Ensure:

The button is listed in CaptureTriggerId
The document was actually edited (check HasEditedDocument)
The callback URL is reachable from OnlyOffice server

PDF conversion fails

Check:

OnlyOffice conversion service is running
The document format is supported for conversion
Network connectivity between your server and OnlyOffice

Next Steps

Now that you have a basic implementation working, explore:

Customizing the editor appearance with CSS
Implementing user permissions and access control
Integrating with your document management system
Adding collaboration features
Implementing version control

API Reference

Explore the complete API documentation

Get Started

Core Concepts

Guides

Examples

Overview

Basic Implementation

Configuring Editor Properties

Basic Configuration

Loading Documents

Advanced Features

PDF Conversion

View-Only Mode

Checking Document Status

Complete Example

Common Patterns

Upload, Edit, and Save Workflow

Load from Database

Troubleshooting

Next Steps

API Reference

Build docs developers (and LLMs) love

Get Started

Core Concepts

Guides

Examples

​Overview

​Basic Implementation

​Configuring Editor Properties

​Basic Configuration

​Loading Documents

​Advanced Features

​PDF Conversion

​View-Only Mode

​Checking Document Status

​Complete Example

​Common Patterns

​Upload, Edit, and Save Workflow

​Load from Database

​Troubleshooting

​Next Steps

API Reference

Build docs developers (and LLMs) love

Overview

Basic Implementation

Configuring Editor Properties

Basic Configuration

Loading Documents

Advanced Features

PDF Conversion

View-Only Mode

Checking Document Status

Complete Example

Common Patterns

Upload, Edit, and Save Workflow

Load from Database

Troubleshooting

Next Steps