Entity Framework Validation confusion - maximum string length of '128' - entity-framework

Question

I'm faced with a confusing problem where in my Edit or Create action result methods, EF4 will throw a DbEntityValidationException with the inner message stating:
The field Body must be a string or
array type with a maximum length of
'128'.
The model in question looks like this:
[Table("tblArticles")]
public class Article
{
[Key]
public int ID { get; set; }
[Required(ErrorMessage="Title must be included")]
public string Title { get; set; }
[AllowHtml]
public string Body { get; set; }
[Required(ErrorMessage="Start Date must be specified")]
[Display(Name="Start Date")]
[DisplayFormat(DataFormatString="dd-mm-yyyy")]
public DateTime? StartDate { get; set; }
[Required(ErrorMessage = "End Date must be specified")]
[Display(Name = "End Date")]
public DateTime? EndDate { get; set; }
public int Priority { get; set; }
public bool Archived { get; set; }
public virtual ICollection<ArticleImage> Images { get; set; }
}
The "Body" field in the actual database is of type Text, so there's no obvious limit there. The data that I'm trying to post is this:
<p>
This is an example to confirm that new articles are looking right.</p>
<p>
<img alt="" src="http://www.google.co.nz/logos/2011/houdini11-sr.jpg"
style="width: 160px; height: 56px; float: left;" /></p>
An example of the Edit method looks like this:
[HttpPost]
public ActionResult Edit(Article article)
{
if (ModelState.IsValid)
{
try
{
articleRepository.Update(article);
}
catch (DbEntityValidationException dbevEx)
{
ErrorSignal.FromCurrentContext().Raise(dbevEx);
ModelState.AddModelError("FORM", dbevEx);
return View("Edit", article);
}
// Other exception handling happens...
}
return RedirectToAction("Index");
}
And finally, the method that actually does the grunt work is:
public void Update(T Entity)
{
dbset.Attach(Entity);
db.Entry(Entity).State = System.Data.EntityState.Modified;
db.Commit();
}
I can't see anything in code or in the database that might be causing the problem, so where else should I look?

Answer 1

Default length of string field in code first is 128. If you are using EF validation it will throw exception. You can extend the size by using:
[StringLength(Int32.MaxValue)]
public string Body { get; set; }
This post became somehow popular so I'm adding second approach which also works:
[MaxLength]
public string Body { get; set; }
StringLengthAttribute is from System.ComponentModel.DataAnnotations assembly and MaxLengthAttribute is from EntityFramework assembly (EF 4.1).

Answer 2

If you get this error using a Model First approach, check the EF Model: it may be simply that a property on the Entity you're updating has the Max Length attribute set.

Answer 3

For Entity Framework 4.3.1, 5.0.0 and 6.2.0, you can use IsMaxLength().
Property(m => m.Body ).IsRequired().IsMaxLength();
Configures the column to allow the maximum length supported by the database provider.
https://learn.microsoft.com/en-us/dotnet/api/system.data.entity.modelconfiguration.configuration.stringcolumnconfiguration.ismaxlength?view=entity-framework-6.2.0

Answer 4

May be you have used
Property(m => m.Body ).IsRequired().HasMaxLength(128);
On your dbcontext class in OnModelCreating.
So change as per your length

Answer 5

For me, [MaxLength] didn't work. I have added below statement to the context.
modelBuilder.Entity<YourModel>().Property(e => e.YourColumn).HasMaxLength(4000);
I have not tried exceeding "4000" limit but I think it can be extended further. You don't have to keep it 128 as the error showed by compiler.