ASP.NET Page Life Cycle: Understanding Page Processing Stages and Events
Learn about the ASP.NET Web Forms page life cycle and how to leverage its events for custom code execution. This guide details the various stages of page processing (initialization, loading, rendering, etc.) and how developers can integrate custom logic at different points in the life cycle.
ASP.NET Page Life Cycle
Understanding the ASP.NET Page Life Cycle
When a user requests an ASP.NET Web Forms page, the page goes through a series of stages or events. Understanding this life cycle is crucial for developers because it allows you to add custom code at different points in the page's processing. This enables you to perform tasks like initializing controls, handling user input, saving data, and rendering the final HTML.
Stages of the ASP.NET Page Life Cycle
Stage | Description |
---|---|
Page Request | The initial request for the page. ASP.NET parses and compiles the page. |
Start | Page properties (Request, Response) are initialized. Request type is determined. |
Initialization | Control UniqueID properties are set; master page is applied. |
Load | Control properties are loaded (if postback). |
PostBack Event Handling | Event handlers are called (if postback); validator controls are validated. |
Rendering | ViewState is saved; the Render method is called for each control. |
Unload | Page and control resources are released. |
ASP.NET Page Life Cycle Events
Event | Typical Use |
---|---|
PreInit |
Before initialization; setting master page, themes, etc. |
Init |
After initialization; reading control properties, setting initial values. |
InitComplete |
After initialization; modifying view state. |
PreLoad |
Before postback data is loaded. |
Load |
Loads page and control data; occurs recursively for child controls. |
Control Events | Handling specific control events (e.g., Button click). |
LoadComplete |
After all controls are loaded. |
PreRender |
Before rendering the page to the client. |
PreRenderComplete |
After DataBind is called on data-bound controls. |
SaveStateComplete |
After view state and control state are saved. |
Render (Method, not an event) |
Renders the control's output to the response stream. |
Unload |
Releases resources; occurs recursively for child controls. |