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# ASP.NET Web Control: CssClass Property The `CssClass` property is a standard property shared by almost all ASP.NET Web server controls. It allows developers to apply Cascading Style Sheets (CSS) classes to a control, enabling clean separation of presentation (styling) and content/logic. --- ## Definition and Usage The `CssClass` property is used to set or return the CSS class (or space-separated classes) associated with a Web server control. When the ASP.NET page is rendered, the server control is converted into standard HTML. The value of the `CssClass` property is rendered as the standard HTML `class` attribute of the resulting HTML element. --- ## Syntax ```xml ``` ### Property Values | Property Value | Description | | :--- | :--- | | `style` | A string value specifying one or more CSS class names to apply to the control. Multiple classes should be separated by spaces (e.g., `CssClass="btn btn-primary"`). | --- ## Code Example The following example demonstrates how to apply a custom CSS class to an ASP.NET `Button` control. ### ASPX Markup ```html

``` ### Rendered HTML Output When the server processes the page, the control is rendered as a standard HTML `` element with the `class` attribute: ```html ``` --- ## Considerations and Best Practices ### 1. Multiple CSS Classes You can apply multiple CSS classes to a single control by separating them with a space, just as you would in standard HTML: ```xml ``` ### 2. Programmatic Manipulation You can dynamically get or set the `CssClass` property in your code-behind file (C# or VB.NET): **C# Example:** ```csharp // Setting a class dynamically Button1.CssClass = "active-button"; // Appending a class dynamically Button1.CssClass += " theme-dark"; ``` ### 3. Interaction with Inline Styles If you define individual style properties directly on the control (such as `ForeColor`, `BackColor`, or `Font-Bold`), ASP.NET will render these as inline styles (`style="..."`). Inline styles generally override styles defined in your external or internal CSS classes due to CSS specificity rules. For cleaner code, it is recommended to manage styles entirely via `CssClass` rather than mixing inline style properties.