# Manipulating Table Cells During the MailMerge Process in .NET C# > This article shows how to manipulate table cells during the mail merge process in .NET C#. The FieldMerged event can be used to manipulate the table cells after they are merged. - **Author:** Bjoern Meyer - **Published:** 2024-12-03 - **Modified:** 2025-11-16 - **Description:** This article shows how to manipulate table cells during the mail merge process in .NET C#. The FieldMerged event can be used to manipulate the table cells after they are merged. - **6 min read** (1016 words) - **Tags:** - ASP.NET - ASP.NET Core - Merge Field - MailMerge - **Web URL:** https://www.textcontrol.com/blog/2024/12/03/manipulating-table-cells-during-the-mailmerge-process-in-net-csharp/ - **LLMs URL:** https://www.textcontrol.com/blog/2024/12/03/manipulating-table-cells-during-the-mailmerge-process-in-net-csharp/llms.txt - **LLMs-Full URL:** https://www.textcontrol.com/blog/2024/12/03/manipulating-table-cells-during-the-mailmerge-process-in-net-csharp/llms-full.txt --- The MailMerge class in TX Text Control is a robust library designed to automate document creation through the process of merging data into templates. It serves as a bridge between structured data (e.g., from databases, JSON, or XML) and dynamic document generation, making it invaluable for applications that require automated document workflows. At its core, the MailMerge class simplifies the complex task of creating professional, data-driven documents by allowing developers to easily merge fields in templates with data sources. Templates are designed using the TX Text Control word processing interface, with merge fields representing dynamic content. ### Merge Blocks Merge blocks are a key concept in TX Text Control's MailMerge class, which allows for the dynamic generation of structured, repeatable content in documents. Merge blocks allow developers to effectively handle repeating data structures such as lists, tables, or nested regions in templates. At a high level, a merge block is a defined section within a template that corresponds to a collection or table of data. During the merge process, MailMerge iterates through the data source, dynamically creating content for each record. These merge blocks can be conditionally rendered, filtered, and sorted using the out-of-the-box functionality of the MailMerge class. ### Code-Level Manipulation But the MailMerge class also allows very detailed, code-level manipulation during the merge process. This includes handling merge events, customizing the merge process, and programmatically controlling the output of the merge operation. This level of control is essential for complex document generation scenarios that require fine-grained control over the merge process. This article describes how to use the FieldMerged event to manipulate a table cell that is returned by the event when the merged field is inside a table cell. For this example, we will use a very simple template consisting of two merge fields and a simple repeating block highlighted in red. ![MailMerge Template in TX Text Control](https://s1-www.textcontrol.com/assets/dist/blog/2024/12/03/a/assets/template1.webp "MailMerge Template in TX Text Control") To merge the template, we will use the following simplified JSON data. ``` [ { "invoice-id": "1", "invoice-date": "2019-01-01", "line-items": [ { "product-id": "1", "quantity": "1", "unit-price": "8" }, { "product-id": "2", "quantity": "2", "unit-price": "200" }, { "product-id": "3", "quantity": "1", "unit-price": "100" }, { "product-id": "4", "quantity": "1", "unit-price": "3" } ] } ] ``` In order to merge this template, the following code will be used: ``` textControl1.Load("template.tx", TXTextControl.StreamType.InternalUnicodeFormat); MailMerge mailMerge = new MailMerge(); mailMerge.TextComponent = textControl1; string jsonData = File.ReadAllText("data.json"); mailMerge.MergeJsonData(jsonData); ``` This results in the following merged document: ![Merged Document in TX Text Control](https://s1-www.textcontrol.com/assets/dist/blog/2024/12/03/a/assets/template2.webp "Merged Document in TX Text Control") ### FieldMerged Event Now let's attach the FieldMerged event to manipulate the merge process. ``` textControl1.Load("template.tx", TXTextControl.StreamType.InternalUnicodeFormat); MailMerge mailMerge = new MailMerge(); mailMerge.TextComponent = textControl1; mailMerge.FieldMerged += MailMerge_FieldMerged; string jsonData = File.ReadAllText("data.json"); mailMerge.MergeJsonData(jsonData); ``` Each time a merge field is merged (successfully or not), this event is invoked. A TableCell is returned if the field is located within a table cell. In this event, we check that the *TableCell* property is not null. If it is not null, we set the background color of the cell. ``` private void MailMerge_FieldMerged(object sender, MailMerge.FieldMergedEventArgs e) { if (e.TableCell != null) { e.TableCell.CellFormat.BackColor = Color.Red; e.TableCell.CellFormat.BottomBorderWidth = 60; e.TableCell.CellFormat.BottomBorderColor = Color.Blue; } } ``` As a result, all merged cells are colored during the merge process. ![Merged Document with Colored Cells in TX Text Control](https://s1-www.textcontrol.com/assets/dist/blog/2024/12/03/a/assets/template3.webp "Merged Document with Colored Cells in TX Text Control") ### Dynamic Cell Colors Let's make this process dynamic by adding some logic. The *CellFilterInstructions* class is used to compare a value with a given value to return a specific color. ``` using System; using System.Drawing; using System.Linq; public class CellFilterInstructions { public double? CompareValue { get; set; } = null; public RelationalOperator? Operator { get; set; } = null; public Color TrueColor { get; set; } = Color.White; public Color FalseColor { get; set; } = Color.White; public enum RelationalOperator { Equals = 0, NotEqual, LessThan, GreaterThan, } // evaluates the instruction and returns the proper color public Color? GetColor(string value) { if (Double.TryParse(ParseToNumber(value), out double dValue) == true) { switch (Operator) { case RelationalOperator.Equals: return (dValue == CompareValue ? TrueColor : FalseColor); case RelationalOperator.NotEqual: return (dValue != CompareValue ? TrueColor : FalseColor); case RelationalOperator.GreaterThan: return (dValue > CompareValue ? TrueColor : FalseColor); case RelationalOperator.LessThan: return (dValue < CompareValue ? TrueColor : FalseColor); default: return null; } } else return null; } private string ParseToNumber(string text) { var numericChars = "0123456789,.".ToCharArray(); return new String(text.Where(c => numericChars.Any(n => n == c)).ToArray()); } } ``` The following code creates a new rule that returns green if the value is greater than 10 and red if it is not. This rule is serialized and stored in the Name property of a table cell. ``` textControl1.Load("template.tx", TXTextControl.StreamType.InternalUnicodeFormat); CellFilterInstructions cellFilterInstructions = new CellFilterInstructions() { CompareValue = 10, Operator = CellFilterInstructions.RelationalOperator.GreaterThan, TrueColor = Color.Green, FalseColor = Color.Red }; textControl1.Tables[1].Cells[2,2].Name = JsonConvert.SerializeObject(cellFilterInstructions); MailMerge mailMerge = new MailMerge(); mailMerge.TextComponent = textControl1; mailMerge.FieldMerged += MailMerge_FieldMerged; string jsonData = File.ReadAllText("data.json"); mailMerge.MergeJsonData(jsonData); ``` In the *FieldMerged* event, this rule is deserted and evaluated. The color returned is then applied to the TableCellFormat of the table cell. ``` private void MailMerge_FieldMerged(object sender, MailMerge.FieldMergedEventArgs e) { // custom field handling if (e.TableCell == null) return; if (e.TableCell.Name != "") { CellFilterInstructions instructions = (CellFilterInstructions)JsonConvert.DeserializeObject( e.TableCell.Name, typeof(CellFilterInstructions)); // retrieve the color Color? color = instructions.GetColor(e.MailMergeFieldAdapter.ApplicationField.Text); // apply the color if (color != null) e.TableCell.CellFormat.BackColor = (Color)color; } } ``` The following screenshot shows the result of this merge process: ![Merged Document with Conditional Cell Colors in TX Text Control](https://s1-www.textcontrol.com/assets/dist/blog/2024/12/03/a/assets/template4.webp "Merged Document with Conditional Cell Colors in TX Text Control") ### Conclusion The MailMerge class in TX Text Control provides a powerful and flexible solution for automating document generation processes. Using merge blocks and code-level manipulation, developers can easily create dynamic, data-driven documents. The FieldMerged event provides fine-grained control over the merge process, allowing developers to customize output based on specific conditions. This level of control is essential for complex document generation scenarios that require precise handling of data and content. --- ## 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 - [Use MailMerge in .NET on Linux to Generate Pixel-Perfect PDFs from DOCX Templates](https://www.textcontrol.com/blog/2025/05/27/use-mailmerge-in-dotnet-on-linux-to-generate-pixel-perfect-pdfs-from-docx-templates/llms.txt) - [Generating Dynamic NDAs Using TX Text Control MailMerge in C# .NET](https://www.textcontrol.com/blog/2025/04/08/generating-dynamic-ndas-using-tx-text-control-mailmerge-in-csharp-dotnet/llms.txt) - [Designing a Maintainable PDF Generation Web API in ASP.NET Core (Linux) C# with Clean Architecture and TX Text Control](https://www.textcontrol.com/blog/2025/03/27/designing-a-maintainable-pdf-generation-web-api-in-asp-net-core-linux-c-sharp-with-clean-architecture-and-tx-text-control/llms.txt) - [When to Generate Documents Server-Side Instead of Client-Side: A Focus on Data Security](https://www.textcontrol.com/blog/2024/10/04/when-to-generate-documents-server-side-instead-of-client-side-a-focus-on-data-security/llms.txt) - 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