ConfigurationManager Migration Shim

This sample demonstrates the ConfigurationManager static shim that allows Web Forms code accessing ConfigurationManager.AppSettings and ConfigurationManager.ConnectionStrings to work in Blazor without code changes.

1. Reading AppSettings

In Web Forms, you'd read app settings from Web.config. The BWFC shim reads from IConfiguration instead, using the "AppSettings" section.

<!-- Web.config -->
<configuration>
  <appSettings>
    <add key="SiteName" value="My Site" />
    <add key="MaxItemsPerPage" value="25" />
  </appSettings>
</configuration>

// Code-behind
var siteName = ConfigurationManager.AppSettings["SiteName"];
var maxItems = ConfigurationManager.AppSettings["MaxItemsPerPage"];

// appsettings.json
{
  "AppSettings": {
    "SiteName": "BlazorWebFormsComponents Demo",
    "MaxItemsPerPage": "25"
  }
}

// Same code works!
var siteName = ConfigurationManager.AppSettings["SiteName"];
var maxItems = ConfigurationManager.AppSettings["MaxItemsPerPage"];

2. Reading ConnectionStrings

Connection strings work the same way — the shim reads from the "ConnectionStrings" section of IConfiguration.

<!-- Web.config -->
<connectionStrings>
  <add name="DefaultConnection" 
       connectionString="Server=..." />
</connectionStrings>

// Code-behind
var connStr = ConfigurationManager
    .ConnectionStrings["DefaultConnection"]
    .ConnectionString;

// appsettings.json
{
  "ConnectionStrings": {
    "DefaultConnection": "Server=..."
  }
}

// Same code works!
var connStr = ConfigurationManager
    .ConnectionStrings["DefaultConnection"]
    .ConnectionString;

3. Setup Required

To enable the ConfigurationManager shim, add this line to your Program.cs after calling UseBlazorWebFormsComponents():

app.UseBlazorWebFormsComponents();
app.UseConfigurationManagerShim();  // Enable ConfigurationManager shim

4. Direct IConfiguration Access (Recommended for New Code)

The ConfigurationManager shim is for migration compatibility. For new Blazor code, inject IConfiguration directly:

@inject IConfiguration Configuration

@code {
    private string siteName = "";
    
    protected override void OnInitialized()
    {
        siteName = Configuration["AppSettings:SiteName"] ?? "";
    }
}