According to this question, there's no built-in way in EF v1 to figure out the length of a field. Is there a built-in way to do so in the Entity Framework that ships with .NET 4, if so - how?
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2 Answers
There is no new way to access the length of a property in EF 4.0. You still have to walk over the metadata - as shown in the accepted answer on the question you reference.
Comments
This acts:
using System;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Data.Metadata.Edm;
using System.Linq;
using System.Linq.Expressions;
namespace EfWidgets
{
public class EntityWidgets
{
public static int GetMaxLength<TEntity>(ObjectContext oc, Expression<Func<TEntity, string>> property)
where TEntity : EntityObject
{
var test = oc.MetadataWorkspace.GetItems(DataSpace.CSpace);
if (test == null)
return -1;
Type entType = typeof(TEntity);
string propertyName = ((MemberExpression)property.Body).Member.Name;
var q = test
.Where(m => m.BuiltInTypeKind == BuiltInTypeKind.EntityType)
.SelectMany(meta => ((EntityType)meta).Properties
.Where(p => p.Name == propertyName && p.TypeUsage.EdmType.Name == "String"));
var queryResult = q.Where(p =>
{
var match = p.DeclaringType.Name == entType.Name;
if (!match)
match = entType.Name == p.DeclaringType.Name;
return match;
})
.Select(sel => sel.TypeUsage.Facets["MaxLength"].Value)
.ToList();
if (queryResult.Any())
{
int result = Convert.ToInt32(queryResult.First());
return result;
}
return -1;
}
}
}
2 Comments
Jan Jurníček
Example of using: maxLength = GetMaxLength<Product>(northwindContext, Product => Product.QuantityPerUnit);
Michael Freidgeim
Is it better than similar( but shorter) method from stackoverflow.com/a/772556/52277 ?