I need to put a max length on my test field on my Views using ASP.NET MVC with the Entity Framework and I can't find how to get the max length of a varchar field.
Is there an easy way to get that, or any other property of a database field
Here is how i manage to do it (with an extension method on entities) :
public static int? GetMaxLength(this EntityObject entite, string nomPropriete)
{
int? result = null;
using (XEntities contexte = XEntities.GetCurrentContext())
{
var queryResult = from meta in contexte.MetadataWorkspace.GetItems(DataSpace.CSpace)
.Where(m => m.BuiltInTypeKind == BuiltInTypeKind.EntityType)
from p in (meta as EntityType).Properties
.Where(p => p.DeclaringType.Name == entite.GetType().Name
&& p.Name == nomPropriete
&& p.TypeUsage.EdmType.Name == "String")
select p.TypeUsage.Facets["MaxLength"].Value;
if (queryResult.Count() > 0)
{
result = Convert.ToInt32(queryResult.First());
}
}
return result;
}
Update
I realize that this answer doesn't directly apply to EF. At the time that I answered, there had been no answers for about 20 minutes and I thought knowing how I solved a similar problem with LINQToSQL might help. Given that the OP basically used the same technique albeit with EF properties instead, seems to indicate that I made the right choice. I'm leaving this answer here for context and for those who get here having the same problem but with LINQToSQL.
Original
I don't know about EF, but LINQToSQL entity properties are decorated with ColumnAttributes. You may be able to get the ColumnAttribute from the PropertyInfo for the property by looking at the CustomAttributesCollection. The value of this attribute would need to be parsed for length. I do that in my validator classes to make sure that I'm not going to get a SQL error by using a string that is too long for my column.
This is the method I use to extract the column length for string properties.
public static int MaximumPropertyLength( Type type, string propertyName )
{
int maximumLength = -1;
PropertyInfo info = type.GetProperty( propertyName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance );
if (info != null)
{
var attribute = info.GetCustomAttributes( typeof( ColumnAttribute ), false )
.Cast<ColumnAttribute>()
.FirstOrDefault();
if (attribute != null)
{
maximumLength = ExtractLength( attribute.DbType );
}
}
return maximumLength;
}
private static int ExtractLength( string dbType )
{
int max = int.MaxValue;
if (dbType.Contains( "(" ))
{
string[] parts = dbType.Split( new char[] { '(', ')' }, StringSplitOptions.RemoveEmptyEntries );
if (parts.Length > 1)
{
int.TryParse( parts[1], out max );
}
}
return max;
}
For EntityFramework you would need to add your own custom attributes to the classes using a Code Generator or T4 Template.
Then what tvanfosson stated above would hold true. EF does not persist this information by default.
http://blogs.msdn.com/adonet/archive/2008/01/24/customizing-code-generation-in-the-ado-net-entity-designer.aspx
Explains more of what I am talking about with your code generator. It is pretty slick I have done exactly what you are mentioning before, problem is with proprietary code so I do not have an example for you.
Related
I have succesfully extended the EF6 designer to allow for some custom properties on my entities, associations and properties using this post:
Extending Entity Framework 6 - adding custom properties to entities in designer
Now I need to use these custom properties when generating code in T4 but I have no clue how to access that information. Can someone point me in the right direction ?
regards,
Jurjen.
I've figured it out.
looking at, for instance, the entity variable in "foreach (var entity in typeMapper.GetItemsToGenerate(itemCollection))", this is a GlobalItem (https://msdn.microsoft.com/en-us/library/system.data.metadata.edm.globalitem(v=vs.110).aspx) wich contains MetadataProperties.
Listing these properties using a simple foreach
foreach( var mp in entity.MetadataProperties)
{
this.WriteLine("{0} = '{1}'", mp.Name, mp.Value);
}
results in a list
Name = 'Role'
NamespaceName = 'Model1'
Abstract = 'False'
...
http://saop.si:RecordTracked = '<a:RecordTracked xmlns:a="http://saop.si">true</a:RecordTracked>'
http://saop.si:DisplayMember = '<a:DisplayMember xmlns:a="http://saop.si">true</a:DisplayMember>'
as you can see, the custom properties (RecordTracked, DisplayName) are listed as well.
I have created 2 functions in within public class CodeStringGenerator to retrieve any custom property. Call it like this :
CodeStringGenerator.GetCustomPropertyAsBoolean(entity, "RecordTracked");
private bool GetCustomPropertyAsBoolean(GlobalItem item, string propertyName)
{
var _value = GetCustomProperty(item, propertyName);
if (string.IsNullOrEmpty(_value ))
{ return false; }
return _value.Equals("true", StringComparison.CurrentCultureIgnoreCase);
}
private string GetCustomProperty(GlobalItem item, string propertyName)
{
var _found = item.MetadataProperties.FirstOrDefault(p => p.Name.StartsWith("http://") &&
p.Name.EndsWith(propertyName, StringComparison.CurrentCultureIgnoreCase ));
if (_found == null)
{ return string.Empty; }
var _value = _found.Value as System.Xml.Linq.XElement;
if (_value == null)
{ return string.Empty; }
return _value.Value;
}
Currently I am doing like this:
For Example:
public update(Person model)
{
// Here model is model return from form on post
var oldobj = db.Person.where(x=>x.ID = model.ID).SingleOrDefault();
db.Entry(oldobj).CurrentValues.SetValues(model);
}
It works, but for example,
I have 50 columns in my table but I displayed only 25 fields in my form (I need to partially update my table, with remaining 25 column retain same old value)
I know it can be achieve by "mapping columns one by one" or by creating "hidden fields for those remaining 25 columns".
Just wondering is there any elegant way to do this with less effort and optimal performance?
This is a very good question. By default I have found that as long as change tracking is enabled (it is by default unless you turn it off), Entity Framework will do a good job of applying to the database only what you ask it to change.
So if you only change 1 field against the object and then call SaveChanges(), EF will only update that 1 field when you call SaveChanges().
The problem here is that when you map a view model into an entity object, all of the values get overwritten. Here is my way of handling this:
In this example, you have a single entity called Person:
Person
======
Id - int
FirstName - varchar
Surname - varchar
Dob - smalldatetime
Now let's say we want to create a view model which will only update Dob, and leave all other fields exactly how they are, here is how I do that.
First, create a view model:
public class PersonDobVm
{
public int Id { get; set; }
public DateTime Dob { get; set; }
public void MapToModel(Person p)
{
p.Dob = Dob;
}
}
Now write the code roughly as follows (you'll have to alter it to match your context name etc):
DataContext db = new DataContext();
Person p = db.People.FirstOrDefault();
// you would have this posted in, but we are creating it here just for illustration
var vm = new PersonDobVm
{
Id = p.Id, // the Id you want to update
Dob = new DateTime(2015, 1, 1) // the new DOB for that row
};
vm.MapToModel(p);
db.SaveChanges();
The MapToModel method could be even more complicated and do all kinds of additional checks before assigning the view model fields to the entity object.
Anyway, the result when SaveChanges is called is the following SQL:
exec sp_executesql N'UPDATE [dbo].[Person]
SET [Dob] = #0
WHERE ([Id] = #1)
',N'#0 datetime2(7),#1 int',#0='2015-01-01 00:00:00',#1=1
So you can clearly see, Entity Framework has not attempted to update any other fields - just the Dob field.
I know in your example you want to avoid coding each assignment by hand, but I think this is the best way. You tuck it all away in your VM so it does not litter your main code, and this way you can cater for specific needs (i.e. composite types in there, data validation, etc). The other option is to use an AutoMapper, but I do not think they are safe. If you use an AutoMapper and spelt "Dob" as "Doob" in your VM, it would not map "Doob" to "Dob", nor would it tell you about it! It would fail silently, the user would think everything was ok, but the change would not be saved.
Whereas if you spelt "Dob" as "Doob" in your VM, the compiler will alert you that the MapToModel() is referencing "Dob" but you only have a property in your VM called "Doob".
I hope this helps you.
I swear by EntityFramework.Extended. Nuget Link
It lets you write:
db.Person
.Where(x => x.ID == model.ID)
.Update(p => new Person()
{
Name = newName,
EditCount = p.EditCount+1
});
Which is very clearly translated into SQL.
Please try this way
public update(Person model)
{
// Here model is model return from form on post
var oldobj = db.Person.where(x=>x.ID = model.ID).SingleOrDefault();
// Newly Inserted Code
var UpdatedObj = (Person) Entity.CheckUpdateObject(oldobj, model);
db.Entry(oldobj).CurrentValues.SetValues(UpdatedObj);
}
public static object CheckUpdateObject(object originalObj, object updateObj)
{
foreach (var property in updateObj.GetType().GetProperties())
{
if (property.GetValue(updateObj, null) == null)
{
property.SetValue(updateObj,originalObj.GetType().GetProperty(property.Name)
.GetValue(originalObj, null));
}
}
return updateObj;
}
I have solved my Issue by using FormCollection to list out used element in form, and only change those columns in database.
I have provided my code sample below; Great if it can help someone else
// Here
// collection = FormCollection from Post
// model = View Model for Person
var result = db.Person.Where(x => x.ID == model.ID).SingleOrDefault();
if (result != null)
{
List<string> formcollist = new List<string>();
foreach (var key in collection.ToArray<string>())
{
// Here apply your filter code to remove system properties if any
formcollist.Add(key);
}
foreach (var prop in result.GetType().GetProperties())
{
if( formcollist.Contains(prop.Name))
{
prop.SetValue(result, model.GetType().GetProperty(prop.Name).GetValue(model, null));
}
}
db.SaveChanges();
}
I still didn't find a nice solution for my problem, so I created a work around. When loading the Entity, I directly make a copy of it and name it entityInit. When saving the Entity, I compare the both to see, what really was changed. All the unchanged Properties, I set to unchanged and fill them with the Database-Values. This was necessary for my Entities without Tracking:
// load entity without tracking
var entityWithoutTracking = Context.Person.AsNoTracking().FirstOrDefault(x => x.ID == _entity.ID);
var entityInit = CopyEntity(entityWithoutTracking);
// do business logic and change entity
entityWithoutTracking.surname = newValue;
// for saving, find entity in context
var entity = Context.Person.FirstOrDefault(x => x.ID == _entity.ID);
var entry = Context.Entry(entity);
entry.CurrentValues.SetValues(entityWithoutTracking);
entry.State = EntityState.Modified;
// get List of all changed properties (in my case these are all existing properties, including those which shouldn't have changed)
var changedPropertiesList = entry.CurrentValues.PropertyNames.Where(x => entry.Property(x).IsModified).ToList();
foreach (var checkProperty in changedPropertiesList)
{
try
{
var p1 = entityWithoutTracking.GetType().GetProperty(checkProperty).GetValue(entityWithoutTracking);
var p2 = entityInit.GetType().GetProperty(checkProperty).GetValue(entityInit);
if ((p1 == null && p2 == null) || p1.Equals(p2))
{
entry.Property(checkProperty).CurrentValue = entry.Property(checkProperty).OriginalValue; // restore DB-Value
entry.Property(checkProperty).IsModified = false; // throws Exception for Primary Keys
}
} catch(Exception) { }
}
Context.SaveChanges(); // only surname will be updated
This is way I did it, assuming the new object has more columns to update that the one we want to keep.
if (theClass.ClassId == 0)
{
theClass.CreatedOn = DateTime.Now;
context.theClasses.Add(theClass);
}
else {
var currentClass = context.theClasses.Where(c => c.ClassId == theClass.ClassId)
.Select(c => new TheClasses {
CreatedOn = c.CreatedOn
// Add here others fields you want to keep as the original record
}).FirstOrDefault();
theClass.CreatedOn = currentClass.CreatedOn;
// The new class will replace the current, all fields
context.theClasses.Add(theClass);
context.Entry(theClass).State = EntityState.Modified;
}
context.SaveChanges();
In EF you can do like this
var result = db.Person.Where(x => x.ID == model.ID).FirstOrDefault();
if(result != null){
result.Name = newName;
result.DOB = newDOB;
db.Person.Update(result);
}
Or you can use
using (var db= new MyDbContext())
{
var result= db.Person.Where(x => x.ID == model.ID).FirstOrDefault();
result.Name= newName;
result.DOB = newDOB;
db.Update(result);
db.SaveChanges();
}
For more detail please EntityFramework Core - Update Only One Field
No Worry guys
Just write raw sql query
db.Database.ExecuteSqlCommand("Update Person set Name='"+_entity.Name+"' where Id = " + _entity.ID + "");
I have the following ActionFilter class, to implement my custom authorization system:-
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class CheckUserPermissionsAttribute : ActionFilterAttribute
{
Repository repository = new Repository();
public string Model { get; set; }
public string Action { get; set; }
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
string ADusername = filterContext.HttpContext.User.Identity.Name.Substring(filterContext.HttpContext.User.Identity.Name.IndexOf("\\") + 1);
if (!repository.can(ADusername,Model,Action))
{
filterContext.Result = new HttpUnauthorizedResult("You cannot access this page");
}
base.OnActionExecuting(filterContext);
}
}
The above class will call the following repository method:-
public bool can(string user, string Model, string Action)
{
bool result;
bool result2;
int size =tms.PermisionLevels.Where(a5 => a5.Name == Action).SingleOrDefault().PermisionSize;
var securityrole = tms.SecurityroleTypePermisions.Where(a => a.PermisionLevel.PermisionSize >= size && a.TechnologyType.Name == Model).Select(a => a.SecurityRole).Include(w=>w.Groups).Include(w2=>w2.SecurityRoleUsers).ToList();
foreach (var item in securityrole)
{
result = item.SecurityRoleUsers.Any(a => a.UserName.ToLower() == user.ToLower());
var no = item.Groups.Select(a=>a.TMSUserGroups.Where(a2=>a2.UserName.ToLower() == user.ToLower()));
result2 = no.Count() == 1;
if (result || result2) {
return true;
}}
return false;
}
But inside my repository method , I am doing the following:-
Query the database and include all the Groups & SecurityRoleUsers when executing the .tolist()
Then filter the returned records insdie the server, based on the foreach loop.
But this will cause the following drawbacks:-
If I have many Groups and SecurityRoleUsers, then I will be getting them all from the DB, and then filter the result on the server.
And since this code will be executed whenever an action method is called, as it Is a security attribute at the begging of the controller class. So this might not be very efficient.
So my question is whether I can join all the queries inside the repository method to be single query , and do all the work on the Database and just return true or false to the server ?
The associated tables looks as follow:-
Ideally remove this foreach.
Try riding with Linq to Sql.
You should be more comfortable because it resembles SQL.
This link has several examples.
http://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b
Att
Julio Spader
wessolucoes.com.br
Use linq.
Ideally you should only have one line of code after you got the size value. e.g.
int size =tms.PermisionLevels.Where(a5 => a5.Name == Action).SingleOrDefault().PermisionSize;
var result = //One line of code to determine user authenticity
return result;
I think you should design you database in the way that join queries are easy to do. So you don't have to perform more than one select.
Try code-first EF, which links tables very easily.
You need to take care with Lazy Loading. If not used correctly, it will make a query to the database each object segmentation, especially in your foreach. With that already has a good improvement.
Take a look at this article. I think it will help you too.
http://www.sql-server-performance.com/2012/entity-framework-performance-optimization/
Att
Julio Spader
wessolucoes.com.br
In EF 4.0, if I understand it right, there are two type of values in Entity : current values and original values.
We can set original values by calling ApplyOriginalValues(TEntity) method but how to get original values ?
#Eranga answer is outdated for EF 5. For some reason, EF 5 doesn't work fine when getting original values using an statement like this:
var originalValues = context.Entry(myEntity).OriginalValues;
My working solution uses AsNoTracking() method from DbSet, like the example below:
var originalEntity = context.MyEntities.AsNoTracking().FirstOrDefault(me => me.MyEntityID == myEntity.MyEntityID);
You can access them through ObjectStateEntry
var originalValues = context
.ObjectStateManager.GetObjectStateEntry(myEntity).OriginalValues;
This could be refined further to the following:
var originalEntity = context.MyEntities.AsNoTracking()
.FirstOrDefault(me => me.MyEntityID == myEntity.MyEntityID);
The Where in the above, good, response is not needed.
var originalEntity = (EntityType)context.Entry(editEntity).OriginalValues.ToObject();
Sorry for my english.
With this way you can get the original entity values in the form of the object entity with no changes on the edit values.
Example:
If you like edit a Person the line in top look like this
var originalPerson = (Person)context.Entry(editPerson).OriginalValues.ToObject();
I ran into a similar problem and AsNoTracking was not an option for my situation so i came up with something that works well enough for me: first "clone" the entity then do changes.
public T Clone<T>(T entity)
where T : class, new() {
var clone = new T();
var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy)
.Where(a => a.CanRead &&
a.CanWrite &&
a.GetMethod.IsFinal);
foreach (var property in properties) {
property.SetValue(clone, property.GetValue(entity));
}
return clone;
}
and then compare the clone to the changed.
public string GenerateChangeText<T>(T original, T current)
where T : class, new() {
var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy)
.Where(a => a.CanRead &&
a.CanWrite &&
a.GetMethod.IsFinal);
var changes = string.Empty;
foreach (var property in properties) {
var originalValue = property.GetValue(original);
var currentValue = property.GetValue(current);
if (originalValue == null && currentValue == null) continue;
if ((originalValue != null && !originalValue.Equals(currentValue)) ||
(currentValue != null && !currentValue.Equals(originalValue))) {
changes += $" changed {property} from {original ?? "NULL"} to {current ?? "NULL"}.";
}
}
return changes;
}
There are a few versions of Entity Framework in use.
I myself prefer Code First and with that API it's easy as
_context.Entry(Entity).Reload();
Docs
https://msdn.microsoft.com/en-us/library/system.data.entity.infrastructure.dbentityentry.reload(v=vs.103).aspx
The older API's have a Refresh method on the ObjectContext which can help in certain use cases
ObjectContext.Refresh(RefreshMode.StoreWins, Entity);
Docs https://msdn.microsoft.com/en-us/library/bb896255(v=vs.110).aspx
This answer refers to Entity Framework 6. In EF 6 there is an Original value and Current value https://msdn.microsoft.com/en-us/library/gg679512(v=vs.113).aspx After looking and not finding a good answer I came up with the following test function and thought I would post it for others needing to do the same.
private void test()
{
// table has a field Description of type varchar(200)
WDMDBEntities context = new WDMDBEntities();
var query = context.Brands;
List<Brand> records = query.ToList();
if (records.Count > 0)
{
Brand currentRecord = records[0];
currentRecord.Description = "some new text";
string originalValue = null;
switch (context.Entry(currentRecord).State)
{
case System.Data.Entity.EntityState.Added:
originalValue = null;
break;
case System.Data.Entity.EntityState.Deleted:
case System.Data.Entity.EntityState.Detached:
case System.Data.Entity.EntityState.Modified:
case System.Data.Entity.EntityState.Unchanged:
originalValue = context.Entry(currentRecord).Property(u => u.Description).OriginalValue;
break;
}
}
context.Dispose();
}
I have an entityframework entity called "ABC" (attributes ID and Title).
On update record view, I have added the ID as hidden field and title is the text box.
Controller looks like something:
public ActionResult UpdateAction( ABC obj )
I get everything fine and fair in obj - i.e., the title, and the ID.
Now to update the record in database, I read the original entity:
var original = (from x in base.context.ABC where x.id == obj.id ).Single();
Now to reflect the changes in original, I think should do the update model:
this.TryUpdateModel( original );
I get an error :| ... stating that column ID cannot be changed.
The property 'id' is part of the object's key information and cannot be modified.
I do not want to manually assign the properties back to original object.
The other alternative can be:
TryUpdateModel(original, new string[] { "Title" }, form.ToValueProvider());
But I hate strings - also, my object has like 20 attributes :|
Can someone please suggest a better pattern of doing so?
Rgds
public class ControllerExt : Controller
{
protected void UpdateModel<TModel>(TModel model, params Expression<Func<TModel, object>>[] property) where TModel : class
{
var props = new List<string>(property.Length);
foreach (var p in property)
{
var memberExpression = RemoveUnary(p.Body) as MemberExpression;
if (memberExpression == null)
{
throw new NullReferenceException("Can not retrieve info about member of {0}".FormatThis(typeof(TModel).Name));
}
props.Add(memberExpression.Member.Name);
}
this.UpdateModel(model, props.ToArray());
}
private static Expression RemoveUnary(Expression body)
{
var unary = body as UnaryExpression;
if (unary != null)
{
return unary.Operand;
}
return body;
}
}
Example:
UpdateModel<MyModel>(model, x => x.PropertyFromMyModel_1, x => x.PropertyFromMyModel_2);