CODEWITHSUNDEEP
c#.netasp.net-mvcentity-frameworkentity-framework-4
BenC3
BenC3

Reputation: 716

Entity Framework: Check all relationships of an entity for foreign key use

I have an entity, let's call it CommonEntity that has a primary key used as a foreign key in many other entities. As the application is developed these links will continue to grow.

I'd like a way to see if CommonEntity can be safely deleted (i.e. it's not used by any other entities).

I realise I can do

if(!ce.EntityA.Any() && !ce.EntityB.Any() ... && !ce.EntityN.Any())
{
   //Delete
}

but I'm hoping for a way to just check all of the relationships automatically, as I don't love the idea of having to come back and change this code manually every time we add a new relationship. Perhaps there is something in EF4+ that I'm not aware of?

I thought it might be possible to use a transaction scope to just try and delete the object and roll it back if it fails, but I wasn't sure if there were any adverse side effects with this approach.

Is there a better approach?

EDIT: Looks like VS2012 has used EF5 even though the project is .Net 4, so it has created the model with POCOs even though it was generated from a DB.

Upvotes: 15

Views: 17058

Answers (4)

Pramod Singh
Pramod Singh

Reputation: 1

First find the entity which you want to delete using Find in EF and pass the entity to below function.. If the function returns true it means cannot be deleted and foreign data exists.. If function returns false it means no parent or child records and can be delete..

 public static bool DeleteCheckOnEntity(object entity)
   {
     var propertiesList = entity.GetType().GetProperties();
     return (from prop in propertiesList where prop.PropertyType.IsGenericType select prop.GetValue(entity) into propValue select propValue as IList).All(propList => propList == null || propList.Count <= 0);
   }

Upvotes: -2

mX64
mX64

Reputation: 388

You can use Reflection for this (if you don't want use "Fail Delete On SQL") I write this because I dont want to DELETE Entity, just want to know if its related to any or not !

 public static object GetEntityFieldValue(this object entityObj, string propertyName)
        {
            var pro = entityObj.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance).First(x => x.Name == propertyName);
            return pro.GetValue(entityObj, null);

        }

 public static IEnumerable<PropertyInfo> GetManyRelatedEntityNavigatorProperties(object entityObj)
        {
            var props = entityObj.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance).Where(x => x.CanWrite && x.GetGetMethod().IsVirtual && x.PropertyType.IsGenericType == true);
            return props;
        }

public static bool HasAnyRelation(object entityObj)
        {

                var collectionProps= GetManyRelatedEntityNavigatorProperties(entityObj);


                foreach (var item in collectionProps)
                {
                    var collectionValue = GetEntityFieldValue(entityObj,item.Name);
                    if (collectionValue != null && collectionValue is IEnumerable)
                    {
                        var col = collectionValue as IEnumerable;
                        if (col.GetEnumerator().MoveNext())
                        {
                            return true;
                        }

                    }
                }
               return false;
}

NOTE that : Context must not Disposed and Proxy Must Be Enabled AND KNOW THAT IT WILL GET ALL RELATED RECORD TO MEMORY (IT'S Too Heavy)

Upvotes: 6

y34h
y34h

Reputation: 1659

Just let it fail. If the entity has many relationships, that verification could be really heavy.

public bool TryDelete(int id)
{
    try
    {
        // Delete
        return true;
    }
    catch (SqlException ex)
    {
        if (ex.Number == 547) return false; // The {...} statement conflicted with the {...} constraint {...}
        throw; // other error
    }
}

Upvotes: 14

user848765
user848765

Reputation:

You can try this:

var allrelatedEnds = ((IEntityWithRelationships)ce).RelationshipManager.GetAllRelatedEnds();
bool hasRelation = false;
foreach (var relatedEnd in allrelatedEnds)
{
    if (relatedEnd.GetEnumerator().MoveNext())
    {
        hasRelation = true;
        break;
    }
}

if (!hasRelation)
{
    //Delete
}

Upvotes: 5

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