Session State Migration

This sample demonstrates the SessionShim that provides Web Forms-compatible Session["key"] access in Blazor. The shim uses ASP.NET Core ISession in SSR mode and falls back to in-memory storage in interactive Blazor Server mode.

1. Setting & Getting Session Values

In Web Forms, you stored values with Session["key"] = value and retrieved them with (string)Session["key"]. The BWFC shim supports the same pattern.

// Store a value
Session["UserName"] = txtName.Text;

// Retrieve a value
var name = (string)Session["UserName"];

// Same code works!
Session["UserName"] = userName;

// Retrieve a value
var name = (string)Session["UserName"];

2. Session.Count

Check how many items are currently stored in the session.

3. Type-Safe Access with Get<T>()

The shim provides Session.Get<T>(key) for strongly-typed retrieval, avoiding manual casts.

// Requires manual cast
var count = (int)Session["ClickCount"];
Session["ClickCount"] = count + 1;

// Type-safe access
var count = Session.Get<int>("ClickCount");
Session["ClickCount"] = count + 1;

4. Clear Session

Call Session.Clear() to remove all session values, just like in Web Forms.

5. Setup Required

The session shim is automatically registered when you call AddBlazorWebFormsComponents(). You also need to enable the session middleware:

// Program.cs
builder.Services.AddBlazorWebFormsComponents(); // registers SessionShim + AddSession()

var app = builder.Build();
app.UseSession();                  // enable session middleware
app.UseBlazorWebFormsComponents();

Then inherit from WebFormsPageBase in your component to access Session:

@inherits WebFormsPageBase

@code {
    protected override void OnInitialized()
    {
        Session["Greeting"] = "Hello from Blazor!";
        var greeting = (string?)Session["Greeting"];
    }
}