1. 确保在 Blazor 项目中安装了 Microsoft.EntityFrameworkCore 和 Microsoft.EntityFrameworkCore.SqlServer 包。

2. 确保在 DbContext 中已指定了正确的数据库连接字符串。

示例：

public class ApplicationDbContext : DbContext
{
    public ApplicationDbContext(DbContextOptions options)
        : base(options)
    {
    }

    public DbSet Users { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True;MultipleActiveResultSets=True");
    }
}

3. 如果 Blazor WebAssembly 项目中需要使用 Entity Framework，则需要在客户端和服务器端项目中分别添加 DbContext，并通过注入方式使用。

示例： 客户端项目：

services.AddHttpClient("Api", client => client.BaseAddress = new Uri("https://localhost:44385/"))
    .AddHttpMessageHandler();

services.AddScoped(sp => sp.GetRequiredService()
    .CreateClient("Api"));

services.AddOidcAuthentication(options =>
{
    options.ProviderOptions.Authority = "https://localhost:44388";
    options.ProviderOptions.ClientId = "blazorwasm";
    options.ProviderOptions.ResponseType = "code";
    options.ProviderOptions.DefaultScopes.Add("email");
});

services.AddAuthorizationCore();

services.AddTransient();

services.AddBlazoredLocalStorage();
services.AddScoped();
services.AddScoped();
services.AddScoped(sp => new HttpClient { BaseAddress = new Uri("https://localhost:44385/") });
services.AddScoped();

services.AddDevExpressBlazor();
services.AddDevExpressChartsBlazor();

服务器项目：

services.AddDbContext(options =>
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

services.AddDefaultIdentity()
    .AddEntityFrameworkStores();

services.AddIdentityServer()
    .AddApiAuthorization();

services.AddAuthentication()
    .AddIdentityServerJwt();

services.AddControllersWithViews();
services.AddRazorPages();