使用Entity Framework加载具有大字符串属性的实体时性能不佳

Question

Given an entity and a DbContext like the following:

public class Entity
{
    public int Id {get;set;}
    public string LargeString {get;set;}
}

public class MyDbContext : DbContext
{
    public DbSet<Entity> Entities {get;set;}
}

And an entity stored in the database with Id 42 and LargeString containing some two megabytes of XML. The following takes half a minute or so, and occasionally gives OutOfMemoryException :

using (var dbContext = new MyDbContext())
{
    var entity = await dbContext.Entities.SingleAsync(e => e.Id == 42);
}

At the same time, the following Dapper query executes in miliseconds:

using (var dbContext = new MyDbContext())
{
    var entity = await dbContext.Database.Connection
        .Query<Entity>("SELECT Id, LargeString FROM Entities WHERE Id = 42")
        .SingleAsync();
}

Is it possible to somehow hint Entity Framework that the LargeString property could be this large (in a way that would make Entity Framework perform acceptable in this scenario).

Answer 1

I had the same issue yesterday. What I did find out is that async operations with Entity Framework is broken or at least very slow. Try using the same operations synchronously:

using (var dbContext = new MyDbContext())
{
    var entity = dbContext.Entities.Single(e => e.Id == 42);
}

Also read the post by rducom here: https://stackoverflow.com/a/28619983/7108481