.Net Core Entity Framework MySQL - string fields store 255 symbols only

Question

I'm creating an application using .Net Core, Entity Framework and MySQL 5.7, on Windows, using Visual Studio 2015. I've created new simple .net-core project in VS2015 for console application using EF. My data model consists of single type, Article, that has ID (int) and Body(string) fields. When I create database doing:

> dotnet ef migrations add initial_migration
> dotnet ef database update

then string field (Article.Body) of my data model gets type VARCHAR(255) in database, no matter what I set in Column attribute [Column(TypeName = "TEXT")], VARCHAR(1000) not works as well. So if I save some long string, it s truncated to 255 characters.

Furthermore, if I go to database settings and alter Body column to type TEXT in MySQL Workbench, then still string is truncated on 255 characters. What am I doing wrong?

I've put all the code (db context, model) in Program.cs for sake of simplicity.

Program.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using MySQL.Data.EntityFrameworkCore.Extensions;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Threading.Tasks;

namespace netcore
{
    public class Program
    {
        public static void Main(string[] args)
        {
            ArticlesContext context = ArticlesContext.Create();

            Article a = new Article();
            a.Body = @"If one puts some long string here, than only first 255 characters will be saved.";

            context.Add(a);
            context.SaveChanges();
        }
    }

    // DB Context
    public class ArticlesContext : DbContext
    {
        private static string _conStr = @"server=localhost;userid=sevka;pwd=12321;port=3306;database=netcore;sslmode=none;";

        public ArticlesContext() : base() { }

        public ArticlesContext(DbContextOptions<ArticlesContext> options)
        : base(options)
        { }

        public static ArticlesContext Create()
        {
            var optionsBuilder = new DbContextOptionsBuilder<ArticlesContext>();
            optionsBuilder.UseMySQL(_conStr);

            //Ensure database creation
            var context = new ArticlesContext(optionsBuilder.Options);
            context.Database.EnsureCreated();

            return context;
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseMySQL(_conStr);
        }

        public DbSet<Article> Articles { get; set; }
    }

    public class Article
    {
        public int ID { get; set; }

        [Column(TypeName = "TEXT")]
        public string Body { get; set; }
    }
}

Project.json

{
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.1",
      "type": "platform"
    },
    "Microsoft.ApplicationInsights.AspNetCore": "1.0.0",
    "Microsoft.AspNetCore.Diagnostics": "1.0.0",
    "Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore": "1.0.0",
    "Microsoft.AspNetCore.Identity.EntityFrameworkCore": "1.0.0",
    "Microsoft.EntityFrameworkCore.Tools": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Logging": "1.0.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "MySQL.Data.Core": "7.0.4-IR-191",
    "MySql.Data.EntityFrameworkCore": "7.0.6-IR31"
  },

  "tools": {
    "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
  },

  "frameworks": {
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }
  },

  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "runtimeOptions": {
    "configProperties": {
      "System.GC.Server": true
    }
  }
}

You aren't not using Fluent API, you can set the column type, also, can you show your code where you set the value for property? — H. Herzl
– H. Herzl, Commented Nov 28, 2016 at 6:13
@H.Herzl, thank you, you're right. I've tried Fluent API after your comment and it worked properly. So it appears that using Data Annotations attributes is not way to go with EF Core? Value for property is set in Main method of Program.cs in the code: context.Add(a); context.SaveChanges(); — Vasiliy
– Vasiliy, Commented Nov 28, 2016 at 10:28
For future visitors, this is the official bug reported on this problem: github.com/aspnet/EntityFramework/issues/8135, which in turn links to bugs.mysql.com/bug.php?id=84423 — Alpha
– Alpha, Commented Jul 10, 2017 at 18:41

H. Herzl · Accepted Answer · 2016-11-28 16:08:08Z

2

According to your feedback, you need to use fluent API instead of data annotations, as I know it's better to use fluent API in EF Core, this can change in future versions.

In your db context you can set the mapping for your entity, something like this:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
  var entity = modelBuilder.Entity<Entity>();

  entity.Property(p => p.Body).HasColumnType("text");

  base.OnModelCreating(modelBuilder);
}

If you want to have a more stylish entity mapping, you can dive into this tutorial: Creating Angular2 Application with ASP.NET Core Template Pack in VS 2015, this tutorial is for EF Core with SQL Server but applies to MySql as well.

answered Nov 28, 2016 at 16:08

H. Herzl

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