ArgumentException: Expression must be writeable [question][blazor][migration][EntityFrameworkCore]

[netyam]

Hey i have a question, i tried to migrate to a database with

Microsoft.EntityFrameworkCore.SqlServer 3.0.0-preview6.19304.10 Microsoft.EntityFrameworkCore.Tools 3.0.0-preview6.19304.10 .NET Core 3.0 SDK 3.0.100-preview6-012264

i used PM> add-migration PM> update-database Migration was okay but when i try to open it through /api/pizzas/getpizzas i got this problem:

System.ArgumentException: Expression must be writeable
Parameter name: left
   at System.Linq.Expressions.Expression.RequiresCanWrite(Expression expression, String paramName)
   at System.Linq.Expressions.Expression.Assign(Expression left, Expression right)
   at System.Linq.Expressions.Expression.MakeBinary(ExpressionType binaryType, Expression left, Expression right, Boolean liftToNull, MethodInfo method, LambdaExpression conversion)
   at System.Linq.Expressions.BinaryExpression.Update(Expression left, LambdaExpression conversion, Expression right)
   at System.Linq.Expressions.ExpressionVisitor.VisitBinary(BinaryExpression node)
   at Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.RelationalShapedQueryCompilingExpressionVisitor.RelationalProjectionBindingRemovingExpressionVisitor.VisitBinary(BinaryExpression binaryExpression)
   at System.Linq.Expressions.BinaryExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitBlockExpressions(ExpressionVisitor visitor, BlockExpression block)
   at System.Linq.Expressions.ExpressionVisitor.VisitBlock(BlockExpression node)
   at System.Linq.Expressions.BlockExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.VisitConditional(ConditionalExpression node)
   at System.Linq.Expressions.ConditionalExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.VisitConditional(ConditionalExpression node)
   at System.Linq.Expressions.ConditionalExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitBlockExpressions(ExpressionVisitor visitor, BlockExpression block)
   at System.Linq.Expressions.ExpressionVisitor.VisitBlock(BlockExpression node)
   at System.Linq.Expressions.BlockExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.VisitBinary(BinaryExpression node)
   at Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.RelationalShapedQueryCompilingExpressionVisitor.RelationalProjectionBindingRemovingExpressionVisitor.VisitBinary(BinaryExpression binaryExpression)
   at System.Linq.Expressions.BinaryExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitBlockExpressions(ExpressionVisitor visitor, BlockExpression block)
   at System.Linq.Expressions.ExpressionVisitor.VisitBlock(BlockExpression node)
   at System.Linq.Expressions.BlockExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitBlockExpressions(ExpressionVisitor visitor, BlockExpression block)
   at System.Linq.Expressions.ExpressionVisitor.VisitBlock(BlockExpression node)
   at System.Linq.Expressions.BlockExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.RelationalShapedQueryCompilingExpressionVisitor.VisitShapedQueryExpression(ShapedQueryExpression shapedQueryExpression)
   at Microsoft.EntityFrameworkCore.Query.Pipeline.ShapedQueryCompilingExpressionVisitor.VisitExtension(Expression extensionExpression)
   at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.Pipeline.QueryCompilationContext2.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery2[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass9_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetEnumerator()
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.System.Collections.IEnumerable.GetEnumerator()
   at System.Text.Json.Serialization.JsonSerializer.HandleEnumerable(JsonClassInfo elementClassInfo, JsonSerializerOptions options, Utf8JsonWriter writer, WriteStack& state)
   at System.Text.Json.Serialization.JsonSerializer.Write(Utf8JsonWriter writer, Int32 flushThreshold, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonSerializer.WriteAsyncCore(Object value, Type type, Stream utf8Json, JsonSerializerOptions options, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

To Reproduce

1. Using Microsoft.EntityFrameworkCore.SqlServer 3.0.0-preview6.19304.10 Microsoft.EntityFrameworkCore.Tools 3.0.0-preview6.19304.10 .NET Core 3.0 SDK 3.0.100-preview6-012264

2. Run this code:

Pizza.cs

using System;
namespace blazor
{
    public enum Spiciness
    {
        None,
        Spicy,
        Hot
    }
    public class Pizza
    {
        public Pizza() { }
        public Pizza(int id, string name, decimal price,
                     Spiciness spiciness)
        {
            this.Id = id;
            this.Name = name ?? throw new ArgumentNullException(nameof(name), "A pizza needs a name!");
            this.Price = price;
            this.Spiciness = spiciness;
        }
        public int Id { get; }
        public string Name { get; }
        public decimal Price { get; }
        public Spiciness Spiciness { get; }
    }
}

PizzaController.cs

using System.Linq;
using Microsoft.AspNetCore.Mvc;

namespace blazor
{
    [Route("api/[controller]")]
    [ApiController]
    public class PizzasController : ControllerBase
    {

        private PizzaPlaceDbContext db;
        public PizzasController(PizzaPlaceDbContext db)
        {
            this.db = db;
        }

        [HttpGet("pizzas")]
        public IQueryable<Pizza> GetPizzas()
        {
            return db.Pizzas;
        }

        [HttpPost("pizzas")]
        public IActionResult InsertPizza([FromBody] Pizza pizza)
        {
            db.Pizzas.Add(pizza);
            db.SaveChanges();
            return Created($"pizzas/{pizza.Id}", pizza);
        }
    }
}

PizzaDbContext.cs

using Microsoft.EntityFrameworkCore;
using blazor.Data;
namespace blazor
{

    public class PizzaPlaceDbContext : DbContext
    {
        public PizzaPlaceDbContext(
          DbContextOptions<PizzaPlaceDbContext> options)
          : base(options)
        { }
        public DbSet<Pizza> Pizzas { get; set; }
        protected override void OnModelCreating(
          ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            var pizzaEntity = modelBuilder.Entity<Pizza>();
            pizzaEntity.HasKey(pizza => pizza.Id);
            pizzaEntity.Property(pizza => pizza.Price)
                       .HasColumnType("money");
            pizzaEntity.Property(pizza => pizza.Name);
            pizzaEntity.Property(pizza => pizza.Spiciness);
        }
    }
}

Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using blazor.Data;

namespace blazor
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            services.AddRazorPages();
            services.AddServerSideBlazor();
            services.AddSingleton<WeatherForecastService>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
                endpoints.MapBlazorHub();
                endpoints.MapFallbackToPage("/_Host");
            });
        }
    }
}

Migration

using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.EntityFrameworkCore.Migrations;

namespace blazor.Migrations
{
    public partial class pizza : Migration
    {
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.CreateTable(
                name: "Pizzas",
                columns: table => new
                {
                    Id = table.Column<int>(nullable: false)
                        .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
                    Name = table.Column<string>(nullable: true),
                    Price = table.Column<decimal>(type: "money", nullable: false),
                    Spiciness = table.Column<int>(nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Pizzas", x => x.Id);
                });
        }

        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropTable(
                name: "Pizzas");
        }
    }
}

4. See error

Expected behavior

Just json of pizzas

[ajcvickers]

@netyam This is an issue with read-only fields. As a workaround, define the fields explicitly and make them not read-only. For example:

private int _id;
public int Id => _id;

For triage: more minimal repro:

public class Pizza
{
    public Pizza() { }
    public Pizza(int id, string name, decimal price)
    {
        Id = id;
        Name = name ?? throw new ArgumentNullException(nameof(name), "A pizza needs a name!");
        Price = price;
    }

    public int Id { get; }
    public string Name { get; }
    public decimal Price { get; }
}

public class PizzaPlaceDbContext : DbContext
{
    public DbSet<Pizza> Pizzas { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        var pizzaEntity = modelBuilder.Entity<Pizza>();
        pizzaEntity.HasKey(pizza => pizza.Id);
        pizzaEntity.Property(pizza => pizza.Price).HasColumnType("money");
        pizzaEntity.Property(pizza => pizza.Name);
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Test;ConnectRetryCount=0");
}

public class Program
{
    public static void Main()
    {
        using (var context = new PizzaPlaceDbContext())
        {
            context.Database.EnsureDeleted();
            context.Database.EnsureCreated();

            context.Add(new Pizza(0, "Cheese", 1.0m));
            context.SaveChanges();
        }

        using (var context = new PizzaPlaceDbContext())
        {
            foreach (var pizza in context.Pizzas)
            {
                Console.WriteLine(pizza.Name);
            }
        }
    }
}

[PeterHimschoot]

@netyam My book "Blazor Revealed" mentions that you should make the properties read-write now :) Actually funny that I encounter this here (since I am experimenting with the latest EF Core). Greetings from Belgium!

[smitpatel]

Fixed in #15995

[smitpatel]

Regression test Query_and_update_using_constructors_with_property_parameters