# Replace Words at the Input Position with Formatted Content from a Web API > Writing assistance and placeholder replacement are advanced features that help users create professional documents. This sample shows how to replace the word at the current input position with content retrieved from a Web API. - **Author:** Bjoern Meyer - **Published:** 2023-07-06 - **Modified:** 2025-11-16 - **Description:** Writing assistance and placeholder replacement are advanced features that help users create professional documents. This sample shows how to replace the word at the current input position with content retrieved from a Web API. - **2 min read** (303 words) - **Tags:** - ASP.NET - ASP.NET Core - Electronic Signatures - PDF - **Web URL:** https://www.textcontrol.com/blog/2023/07/06/replace-words-at-the-input-position-with-formatted-content-from-a-web-api/ - **LLMs URL:** https://www.textcontrol.com/blog/2023/07/06/replace-words-at-the-input-position-with-formatted-content-from-a-web-api/llms.txt - **LLMs-Full URL:** https://www.textcontrol.com/blog/2023/07/06/replace-words-at-the-input-position-with-formatted-content-from-a-web-api/llms-full.txt - **GitHub Repository:** https://github.com/TextControl/TextControl.Web.Core.MVC.ReplaceWord --- Writing assistance features significantly speed up the writing process by providing auto-correction, auto-completion, and key phrase replacement, saving time and reducing errors to create a professional document or letter. In particular, pre-designed and phrased sentences that are inserted frequently improve the user experience of such applications. This sample shows how to replace the word at the current input position with content retrieved from a Web API. ### Web API To simulate the phrase replacement, the following Web API method *ReplaceWord* accepts a string and returns a value from a dictionary: ``` [HttpGet] public IActionResult ReplaceWord(string word) { Dictionary dict = new Dictionary() { { "Word1", "Formatted replacement for Word1" }, { "Word2", "Formatted replacement for Word2" }, { "Word3", "Formatted replacement for Word3" } }; return dict.ContainsKey(word) ? Ok(dict[word]) : Ok(null); } ``` This Web API method is called from JavaScript in the asynchronous method *replaceWord*: ``` function replaceWord(word) { return new Promise(resolve => { $.get("home/replaceWord", { word: word }) .done(data => resolve(data)) .fail(() => resolve(null)); }); } ``` ### Replacing the Selection When the user presses F8, the word at the input position is selected and retrieved. This word is then sent to the Web API to retrieve the replacement string. This string will eventually be loaded into the selection to replace the current string. ``` TXTextControl.addEventListener("textControlLoaded", async function () { document.addEventListener("keydown", logKey); async function logKey(e) { if (e.key === "F8") { const text = await getTextFromSelection(); const replacedText = await replaceWord(text); if (replacedText !== undefined) { await loadReplacedText(replacedText); } } } function getTextFromSelection() { return new Promise(resolve => { TXTextControl.selectWord(() => { TXTextControl.selection.getText(text => resolve(text)); }); }); } async function loadReplacedText(replacedText) { const encodedText = btoa(replacedText); await TXTextControl.selection.load(TXTextControl.StreamType.HTMLFormat, encodedText); } }); ``` The following screen video shows the replacement in action. ![Phrase replacement](https://s1-www.textcontrol.com/assets/dist/blog/2023/07/06/a/assets/replace.gif "Phrase replacement") You can test this yourself by downloading the Visual Studio project from our GitHub repository. --- ## About Bjoern Meyer As CEO, Bjoern is the visionary behind our strategic direction and business development, bridging the gap between our customers and engineering teams. His deep passion for coding and web technologies drives the creation of innovative products. If you're at a tech conference, be sure to stop by our booth - you'll most likely meet Bjoern in person. With an advanced graduate degree (Dipl. Inf.) in Computer Science, specializing in AI, from the University of Bremen, Bjoern brings significant expertise to his role. In his spare time, Bjoern enjoys running, paragliding, mountain biking, and playing the piano. - [LinkedIn](https://www.linkedin.com/in/bjoernmeyer/) - [X](https://x.com/txbjoern) - [GitHub](https://github.com/bjoerntx) --- ## Related Posts - [Preparing Documents for Electronic Signatures using MailMerge in C#](https://www.textcontrol.com/blog/2023/07/05/preparing-documents-for-electronic-signatures-using-mailmerge-in-csharp/llms.txt) - [Why Structured E-Invoices Still Need Tamper Protection using C# and .NET](https://www.textcontrol.com/blog/2026/03/24/why-structured-e-invoices-still-need-tamper-protection-using-csharp-and-dotnet/llms.txt) - [Create Fillable PDFs from HTML Forms in C# ASP.NET Core Using a WYSIWYG Template](https://www.textcontrol.com/blog/2026/03/17/create-fillable-pdfs-from-html-forms-in-csharp-aspnet-core-using-a-wysiwyg-template/llms.txt) - [Why HTML to PDF Conversion is Often the Wrong Choice for Business Documents in C# .NET](https://www.textcontrol.com/blog/2026/03/13/why-html-to-pdf-conversion-is-often-the-wrong-choice-for-business-documents-in-csharp-dot-net/llms.txt) - 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