In Blazor, the StateHasChanged method is used to notify the framework that a component’s state has changed and that it needs to be re-rendered. This method is typically called by the component itself when its state has changed, but it can also be called by other components or services that need to trigger a re-rendering of the component.

When a component’s state changes, Blazor will automatically update the component’s UI to reflect the new state. However, there are certain cases where Blazor may not detect a state change, such as when the state is changed in an asynchronous method or when the state change is triggered by an external event. In these cases, calling StateHasChanged manually is necessary to force Blazor to re-render the component.

For example, suppose you have a component that fetches data from a remote API and displays it in the UI. When the data is received, the component updates its state and triggers a re-rendering of the UI. However, if the data fetching is done in an asynchronous method, Blazor may not automatically detect the state change and the UI may not update. In this case, you can call StateHasChanged after the state change to ensure that the UI is updated.