--- title: "Working with Content Controls in C#" --- {{% alert color="grey" %}} ## Purpose Summary This page explains how to work with content controls conceptually and programmatically. {{% /alert %}} LINQ Reporting Engine enables you to perform certain operations on content controls dynamically while building a report. **Note** – To work with content controls in template documents using Microsoft Word®, you may need to [show the Developer tab on its ribbon](https://docs.microsoft.com/en-us/visualstudio/vsto/how-to-show-the-developer-tab-on-the-ribbon?view=vs-2022). ## Setting Checkbox Values Dynamically You can set checkbox values to either checked or unchecked in your reports dynamically by taking the following steps: 1. Add a checkbox content control to your template at a place where you want it to appear in a result document. 1. By editing content control properties, add a `check` tag to the title of the checkbox content control using the following syntax. {{< highlight csharp >}} <> {{< /highlight >}} Here, `conditional_expression` defines a condition upon which the value of the checkbox content control is to be set to checked (or unchecked, if the condition is not met). The conditional expression must return a `Boolean` value. While building a report, a conditional expression declared within a `check` tag is evaluated and the value of its containing checkbox content control is set accordingly. The `check` tag itself is removed then. ## Adding Combobox and Dropdown List Items Dynamically You can dynamically add items to comboboxes and dropdown lists defined in your template by taking the following steps: 1. Add a combobox or dropdown list content control to your template at a place where you want it to appear in a result document. 2. By editing content control properties, add an item tag to the title of this content control using the following syntax. {{< highlight csharp >}} <> {{< /highlight >}} Here, `value_expression` defines a value of a combobox or dropdown list item to be added dynamically. This expression is mandatory and must return a non‑empty value. In turn, `display_name_expression` defines a display name of the combobox or dropdown list item to be added. This expression is optional. If it is omitted, then during runtime, a value of `value_expression` is used as a display name as well. **Note** – Values of both `value_expression` and `display_name_expression` can be of any types. During runtime, `Object.ToString()` is invoked to get textual representations of these expressions’ values. While building a report, `value_expression` and `display_name_expression` are evaluated and a corresponding combobox or dropdown list item is added. A declaring item tag is removed then. A single `item` tag causes addition of a single combobox or dropdown list item during runtime. You can add multiple combobox or dropdown list items using multiple `item` tags as shown in the following snippet. {{< highlight csharp >}} <><> {{< /highlight >}} Also, you can normally use `item` tags within data bands to add a combobox or dropdown list item per item of a data collection. For example, given that `clients` is a `DataTable` instance having a field named “Name”, you can use the following template to cover such a scenario. {{< highlight csharp >}} <><><> {{< /highlight >}} An `item` tag can also be combined with an `if` tag to add a combobox or dropdown list item depending on a condition as shown in the following snippet. {{< highlight csharp >}} <><><> {{< /highlight >}} Existing combobox and dropdown list items are not affected by `item` tags. Thus, you can combine both ways of adding combobox and dropdown list items using a template: static and dynamic. **Note** – While inserting a combobox or dropdown list, Microsoft Word adds a default item that has to be removed manually, if the item is unwanted. ## Setting Content Control Titles Dynamically You can normally use common expression tags in content control titles, thus forming their contents dynamically. For example, given that `s` is a string value, you can set a content control title from this value dynamically by putting the following expression tag into the title. {{< highlight csharp >}} <<[s]>> {{< /highlight >}} ------ ## FAQ 1. **Q:** How do I make a checkbox content control checked or unchecked based on data? **A:** Add a `check` tag to the checkbox title using the syntax `<>`. The expression must return a Boolean value; if true, the checkbox is checked, otherwise it remains unchecked. The `check` tag is removed automatically after evaluation. 2. **Q:** What is the correct way to add items to a combobox or dropdown list at runtime? **A:** Use the `item` tag inside the content control title: `<>`. The first argument supplies the item value (required), and the optional second argument supplies the display text. Multiple `item` tags can be placed sequentially or generated inside a `foreach` loop. 3. **Q:** Can I conditionally add a combobox item only when a certain condition is met? **A:** Yes. Wrap the `item` tag inside an `if` tag, e.g., `<> <> <>`. The `item` will be added only if the condition evaluates to true. 4. **Q:** Why does a default item appear in a newly inserted dropdown list, and how can I remove it? **A:** Microsoft Word automatically inserts a placeholder item when a dropdown list is created. This item is not removed by Aspose.Words, so you must delete it manually in the template or programmatically after the document is generated. 5. **Q:** How can I set the title of a content control dynamically using a variable? **A:** Place an expression tag inside the title, such as `<<[myVariable]>>`. During report generation the variable’s `ToString()` value replaces the tag, producing a dynamic title. This works for any content control type.