All of my entities (that are mapped to a database table) inherit from an entity class with a dynamic component on it called Attributes e.g.:
public abstract class Entity<T> {
public virtual T Id { get; set; }
private IDictionary _attributes;
public virtual IDictionary Attributes {
get { return _attributes ?? (_attributes = new Hashtable()); }
set { _attributes = value; }
}
}
The Attributes collection allows me to add extra fields to each entity without directly changing the entity itself. This allows me to make my application more modular.
For example say I have the following entity:
public class User : Entity<int> {
public virtual string Name { get; set; }
}
Now say I have a Forum module which needs a NumPosts property against the User. I would add the field against the Users table in the database. This field is non nullable and has a default value of 0. I then map the field using the dynamic component against the User entity.
However when I try inserting the user by saying:
session.Save(new User() { Name = "Test" });
It throws an error as it's expecting me to set a value for NumPosts and the generated SQL would be something like:
INSERT INTO Users (Name, NumPosts) VALUES ('Test', NULL)
However NumPosts does not allow nulls and hence the error. Ideally I'd like it to say the following if the Attributes collection does not contain an entry for NumPosts:
INSERT INTO Users (Name) VALUES ('Test')
An alternative is to say the following which would work fine:
session.Save(new User() { Name = "Test", Attributes = new Hashtable() { { "NumPosts", 0 } } });
The problem I have is that I don't want the modules to have a dependency on each other and I can't really say this.
For reference here's a bare bones version of session factory method which maps the NumPosts field:
return Fluently.Configure()
...
.ExposeConfiguration(c => {
// Get the persistent class
var persistentClass = c.GetClassMapping("User");
// Create the attributes component
var component = new Component(persistentClass);
// Create a simple value
var simpleValue = new SimpleValue(persistentClass.Table);
// Set the type name
simpleValue.TypeName = "Int32";
// Create a new db column specification
var column = new Column("NumPosts");
column.Value = simpleValue;
column.Length = 10;
column.IsNullable = false;
column.DefaultValue = "0";
// Add the column to the value
simpleValue.AddColumn(column);
// Ad the value to the component
component.AddProperty(new Property() { Name = column.Name, Value = simpleValue });
// Add the component property
persistentClass.AddProperty(new Property() { Name = "Attributes", Value = component });
})
.BuildConfiguration();
I'd appreciate if someone could let me know if this is possible. Thanks
You know how to make it working as described above:
... An alternative is to say the following which would work fine:
session.Save(new User()
{
Name = "Test", Attributes = new Hashtable() { { "NumPosts", 0 } }
});
... The problem I have is that I don't want the modules to have a dependency on each other and I can't really say this...
In case, that the biggest issue is the explicit Attributes initialization ("...I don't want the modules to have a dependency...") we can use:
12.2. Event system
So, with Listener like this:
[Serializable]
public class MyPersistListener : NHibernate.Event.ISaveOrUpdateEventListener
{
public void OnSaveOrUpdate(SaveOrUpdateEvent #event)
{
var entity = #event.Entity as Entity<int>; // some interface IHaveAttributes
if (entity == null) // would be more appropriate
{
return;
}
var numPosts = entity.Attributes["NumPosts"] as int?;
if (numPosts.HasValue)
{
return;
}
entity.Attributes["NumPosts"] = 0;
}
}
Based on this doc snippet:
Configuration cfg = new Configuration();
ILoadEventListener[] stack = new ILoadEventListener[] { new MyLoadListener(), new DefaultLoadEventListener() };
cfg.EventListeners.LoadEventListeners = stack;
This should be the init in our case:
.ExposeConfiguration(c => {
var stack = new ISaveOrUpdateEventListener [] { new MyPersistListener() };
c.EventListeners.SaveEventListeners= stack;
I've been Following this post To get my head around Lazy field of T, Which I think I understand, But I'm having trouble getting associated Field Data for a Part loaded this way
Aim - To show photo of blog post author on a blog post.
I want to add a content part "Content Author"
The part Editor should appear as a drop down list of orchard users.
(regardless of the content owner cms users should be able to pick the author)
I have added an image upload field to the User Content Type
I want to show the image of the user on the front end in the view for the Content Author Part
For the first part I have created the content type and used the lazy Filed of UserPart to get the username. However when I try and get the associated fields for the UserPart. There dosent seem to be any.
public class ContentAuthorRecord : ContentPartRecord
{
public virtual string AuthorEmail { get; set; }
}
public class ContentAuthorPart : ContentPart<ContentAuthorRecord>
{
internal readonly LazyField<UserPart> Owner = new LazyField<UserPart>();
public string AuthorEmail
{
get { return Record.AuthorEmail; }
set { Record.AuthorEmail = value; }
}
public UserPart Author
{
get { return Owner.Value; }
set { Owner.Value = value; }
}
public string AuthorName
{
get
{
if (Author == null)
return "Riders for health";
else
{
return Author.UserName;
}
}
}
}
public class ContentAuthorHandler :ContentHandler
{
private readonly IContentManager _contentManager;
public ContentAuthorHandler(IRepository<ContentAuthorRecord> repository, IContentManager contentManager)
{
_contentManager = contentManager;
OnActivated<ContentAuthorPart>(SetUpCustomPart);
Filters.Add(StorageFilter.For(repository));
}
private void SetUpCustomPart(ActivatedContentContext content, ContentAuthorPart part)
{
// Setup the getter of the lazy field
part.Owner.Loader(() => _contentManager.Query<UserPart, UserPartRecord>().List().FirstOrDefault(x => x.Email == part.AuthorEmail));
}
}
I would expect to be able to access the field with something like
(ImageUploadField.Fields.ImageUploadField)Author.Fields.FirstOrDefault(x
=> x.Name == "Photo");
form the within the part class
( although this makes every thing a bit brittle, hard coding a field name, but I'm not sure how eles to go about it)
Further Info
I have a HeaderPart with a Image field added via the cms (not in code) in the display handler I fetch the field like this
protected override DriverResult Display(HeaderPart part, string displayType, dynamic shapeHelper)
{
if (part.HeaderType == HeaderType.Full_width_hero_image)
{
var field = (ImageUploadField) part.Fields.FirstOrDefault(f => f.Name == "HeaderImage");
if (field != null)
{
return ContentShape("Parts_Header_ImageHero",
() => shapeHelper.Parts_Header_ImageHero(ImagePath: field.ImagePath, ImageTitle: field.FileName));
}
return null;
}
if (part.HeaderType == HeaderType.Full_width_hero_video)
{
return ContentShape("Parts_Header_VideoHero", () => shapeHelper.Parts_Header_VideoHero(VideoUrl: part.VideoUrl));
}
if (part.HeaderType == HeaderType.Body_width_video)
{
return ContentShape("Parts_Header_VideoBody", () => shapeHelper.Parts_Header_VideoBody(VideoUrl: part.VideoUrl));
}
return null;
}
This works, But I can do the same for a part loaded into a lazy field.
Cast to dynamic first, then the syntax becomes much simpler: ((dynamic)part.ContentItem).NameOfTheType.NameOfTheField.NameOfTheProperty
If you have added the fields to the User content type via the CMS interface, it may have added the fields to a different part to the one you expect. If you are adding fields to the User content type, by default it will have added the fields to a new part called 'User', not 'UserPart'. Try to following to search all parts in the content item:
(ImageUploadField.Fields.ImageUploadField)Author.ContentItem.Parts
.SelectMany(p => p.Fields).FirstOrDefault(f => f.Name == "Photo");
or directly from the 'User' part:
(ImageUploadField.Fields.ImageUploadField)Author.ContentItem.Parts
.First(p => p.PartDefinition.Name == p.ContentItem.ContentType).Fields
.FirstOrDefault(f => f.Name == "Photo");
I'm having a Entity-Set Countries, reflecting a database table '<'char(2),char(3),nvarchar(50> in my database.
Im having a parser that returns a Country[] array of parsed countries, and is having issues with getting it updated in the right way. What i want is: Take the array of countries, for those countries not already in the database insert them, and those existing update if any fields is different. How can this be done?
void Method(object sender, DocumentLoadedEvent e)
{
var data = e.ParsedData as Country[];
using(var db = new DataContractEntities)
{
//Code missing
}
}
I was thinking something like
for(var c in data.Except(db.Countries)) but it wount work as it compares on wronge fields.
Hope anyone have had this issues before, and have a solution for me. If i cant use the Country object and insert/update an array of them easy, i dont see much benefict of using the framework, as from performers i think its faster to write a custom sql script that inserts them instead of ect checking if an country is already in the database before inserting?
Solution
See answer of post instead.
I added override equals to my country class:
public partial class Country
{
public override bool Equals(object obj)
{
if (obj is Country)
{
var country = obj as Country;
return this.CountryTreeLetter.Equals(country.CountryTreeLetter);
}
return false;
}
public override int GetHashCode()
{
int hash = 13;
hash = hash * 7 + (int)CountryTreeLetter[0];
hash = hash * 7 + (int)CountryTreeLetter[1];
hash = hash * 7 + (int)CountryTreeLetter[2];
return hash;
}
}
and then did:
var data = e.ParsedData as Country[];
using (var db = new entities())
{
foreach (var item in data.Except(db.Countries))
{
db.AddToCountries(item);
}
db.SaveChanges();
}
I would do it straightforward:
void Method(object sender, DocumentLoadedEvent e)
{
var data = e.ParsedData as Country[];
using(var db = new DataContractEntities)
{
foreach(var country in data)
{
var countryInDb = db.Countries
.Where(c => c.Name == country.Name) // or whatever your key is
.SingleOrDefault();
if (countryInDb != null)
db.Countries.ApplyCurrentValues(country);
else
db.Countries.AddObject(country);
}
db.SaveChanges();
}
}
I don't know how often your application must run this or how many countries your world has. But I have the feeling that this is nothing where you must think about sophisticated performance optimizations.
Edit
Alternative approach which would issue only one query:
void Method(object sender, DocumentLoadedEvent e)
{
var data = e.ParsedData as Country[];
using(var db = new DataContractEntities)
{
var names = data.Select(c => c.Name);
var countriesInDb = db.Countries
.Where(c => names.Contains(c.Name))
.ToList(); // single DB query
foreach(var country in data)
{
var countryInDb = countriesInDb
.SingleOrDefault(c => c.Name == country.Name); // runs in memory
if (countryInDb != null)
db.Countries.ApplyCurrentValues(country);
else
db.Countries.AddObject(country);
}
db.SaveChanges();
}
}
The modern form, using later EF versions would be:
context.Entry(record).State = (AlreadyExists ? EntityState.Modified : EntityState.Added);
context.SaveChanges();
AlreadyExists can come from checking the key or by querying the database to see whether the item already exists there.
You can implement your own IEqualityComparer<Country> and pass that to the Except() method. Assuming your Country object has Id and Name properties, one example of that implementation could look like this:
public class CountryComparer : IEqualityComparer<Country>
{
public bool Equals(Country x, Country y)
{
return x.Name.Equals(y.Name) && (x.Id == y.Id);
}
public int GetHashCode(Country obj)
{
return string.Format("{0}{1}", obj.Id, obj.Name).GetHashCode();
}
}
and use it as
data.Countries.Except<Country>(db, new CountryComparer());
Although, in your case it looks like you just need to extract new objects, you can use var newCountries = data.Where(c => c.Id == Guid.Empty); if your Id is Guid.
The best way is to inspect the Country.EntityState property and take actions from there regarding on value (Detached, Modified, Added, etc.)
You need to provide more information on what your data collection contains i.e. are the Country objects retrieved from a database through the entityframework, in which case their context can be tracked, or are you generating them using some other way.
I am not sure this will be the best solution but I think you have to get all countries from DB then check it with your parsed data
void Method(object sender, DocumentLoadedEvent e)
{
var data = e.ParsedData as Country[];
using(var db = new DataContractEntities)
{
List<Country> mycountries = db.Countries.ToList();
foreach(var PC in data)
{
if(mycountries.Any( C => C.Name==PC.Name ))
{
var country = mycountries.Any( C => C.Name==PC.Name );
//Update it here
}
else
{
var newcountry = Country.CreateCountry(PC.Name);//you must provide all required parameters
newcountry.Name = PC.Name;
db.AddToCountries(newcountry)
}
}
db.SaveChanges();
}
}
Here's the table
Users
UserId
UserName
Password
EmailAddress
and the code..
public void ChangePassword(int userId, string password){
//code to update the password..
}
Ladislav's answer updated to use DbContext (introduced in EF 4.1):
public void ChangePassword(int userId, string password)
{
var user = new User() { Id = userId, Password = password };
using (var db = new MyEfContextName())
{
db.Users.Attach(user);
db.Entry(user).Property(x => x.Password).IsModified = true;
db.SaveChanges();
}
}
You can tell entity-framework which properties have to be updated in this way:
public void ChangePassword(int userId, string password)
{
var user = new User { Id = userId, Password = password };
using (var context = new ObjectContext(ConnectionString))
{
var users = context.CreateObjectSet<User>();
users.Attach(user);
context.ObjectStateManager.GetObjectStateEntry(user)
.SetModifiedProperty("Password");
context.SaveChanges();
}
}
In Entity Framework Core, Attach returns the entry, so all you need is:
var user = new User { Id = userId, Password = password };
db.Users.Attach(user).Property(x => x.Password).IsModified = true;
db.SaveChanges();
You have basically two options:
go the EF way all the way, in that case, you would
load the object based on the userId provided - the entire object gets loaded
update the password field
save the object back using the context's .SaveChanges() method
In this case, it's up to EF how to handle this in detail. I just tested this, and in the case I only change a single field of an object, what EF creates is pretty much what you'd create manually, too - something like:
`UPDATE dbo.Users SET Password = #Password WHERE UserId = #UserId`
So EF is smart enough to figure out what columns have indeed changed, and it will create a T-SQL statement to handle just those updates that are in fact necessary.
you define a stored procedure that does exactly what you need, in T-SQL code (just update the Password column for the given UserId and nothing else - basically executes UPDATE dbo.Users SET Password = #Password WHERE UserId = #UserId) and you create a function import for that stored procedure in your EF model and you call this function instead of doing the steps outlined above
i'm using this:
entity:
public class Thing
{
[Key]
public int Id { get; set; }
public string Info { get; set; }
public string OtherStuff { get; set; }
}
dbcontext:
public class MyDataContext : DbContext
{
public DbSet<Thing > Things { get; set; }
}
accessor code:
MyDataContext ctx = new MyDataContext();
// FIRST create a blank object
Thing thing = ctx.Things.Create();
// SECOND set the ID
thing.Id = id;
// THIRD attach the thing (id is not marked as modified)
db.Things.Attach(thing);
// FOURTH set the fields you want updated.
thing.OtherStuff = "only want this field updated.";
// FIFTH save that thing
db.SaveChanges();
While searching for a solution to this problem, I found a variation on GONeale's answer through Patrick Desjardins' blog:
public int Update(T entity, Expression<Func<T, object>>[] properties)
{
DatabaseContext.Entry(entity).State = EntityState.Unchanged;
foreach (var property in properties)
{
var propertyName = ExpressionHelper.GetExpressionText(property);
DatabaseContext.Entry(entity).Property(propertyName).IsModified = true;
}
return DatabaseContext.SaveChangesWithoutValidation();
}
"As you can see, it takes as its second parameter an expression of a
function. This will let use this method by specifying in a Lambda
expression which property to update."
...Update(Model, d=>d.Name);
//or
...Update(Model, d=>d.Name, d=>d.SecondProperty, d=>d.AndSoOn);
( A somewhat similar solution is also given here: https://stackoverflow.com/a/5749469/2115384 )
The method I am currently using in my own code, extended to handle also (Linq) Expressions of type ExpressionType.Convert. This was necessary in my case, for example with Guid and other object properties. Those were 'wrapped' in a Convert() and therefore not handled by System.Web.Mvc.ExpressionHelper.GetExpressionText.
public int Update(T entity, Expression<Func<T, object>>[] properties)
{
DbEntityEntry<T> entry = dataContext.Entry(entity);
entry.State = EntityState.Unchanged;
foreach (var property in properties)
{
string propertyName = "";
Expression bodyExpression = property.Body;
if (bodyExpression.NodeType == ExpressionType.Convert && bodyExpression is UnaryExpression)
{
Expression operand = ((UnaryExpression)property.Body).Operand;
propertyName = ((MemberExpression)operand).Member.Name;
}
else
{
propertyName = System.Web.Mvc.ExpressionHelper.GetExpressionText(property);
}
entry.Property(propertyName).IsModified = true;
}
dataContext.Configuration.ValidateOnSaveEnabled = false;
return dataContext.SaveChanges();
}
New EF Core 7 native feature — ExecuteUpdate:
Finally! After a long wait, EF Core 7.0 now has a natively supported way to run UPDATE (and also DELETE) statements while also allowing you to use arbitrary LINQ queries (.Where(u => ...)), without having to first retrieve the relevant entities from the database: The new built-in method called ExecuteUpdate — see "What's new in EF Core 7.0?".
ExecuteUpdate is precisely meant for these kinds of scenarios, it can operate on any IQueryable instance, and lets you update specific columns on any number of rows, while always issuing a single UPDATE statement behind the scenes, making it as efficient as possible.
Usage:
Let's take OP's example — i.e. updating the password column of a specific user:
dbContext.Users
.Where(u => u.Id == someId)
.ExecuteUpdate(b =>
b.SetProperty(u => u.Password, "NewPassword")
);
As you can see, calling ExecuteUpdate requires you to make calls to the SetProperty method, to specify which property to update, and also what new value to assign to it.
EF Core will translate this into the following UPDATE statement:
UPDATE [u]
SET [u].[Password] = "NewPassword"
FROM [Users] AS [u]
WHERE [u].[Id] = someId
Also, ExecuteDelete for deleting rows:
There's also a counterpart to ExecuteUpdate called ExecuteDelete, which, as the name implies, can be used to delete a single or multiple rows at once without having to first fetch them.
Usage:
// Delete users that haven't been active in 2022:
dbContext.Users
.Where(u => u.LastActiveAt.Year < 2022)
.ExecuteDelete();
Similar to ExecuteUpdate, ExecuteDelete will generate DELETE SQL statements behind the scenes — in this case, the following one:
DELETE FROM [u]
FROM [Users] AS [u]
WHERE DATEPART(year, [u].[LastActiveAt]) < 2022
Other notes:
Keep in mind that both ExecuteUpdate and ExecuteDelete are "terminating", meaning that the update/delete operation will take place as soon as you call the method. You're not supposed to call dbContext.SaveChanges() afterwards.
If you're curious about the SetProperty method, and you're confused as to why ExectueUpdate doesn't instead receive a member initialization expression (e.g. .ExecuteUpdate(new User { Email = "..." }), then refer to this comment (and the surrounding ones) on the GitHub issue for this feature.
Furthermore, if you're curious about the rationale behind the naming, and why the prefix Execute was picked (there were also other candidates), refer to this comment, and the preceding (rather long) conversation.
Both methods also have async equivalents, named ExecuteUpdateAsync, and ExecuteDeleteAsync respectively.
In EntityFramework Core 2.x there is no need for Attach:
// get a tracked entity
var entity = context.User.Find(userId);
entity.someProp = someValue;
// other property changes might come here
context.SaveChanges();
Tried this in SQL Server and profiling it:
exec sp_executesql N'SET NOCOUNT ON;
UPDATE [User] SET [someProp] = #p0
WHERE [UserId] = #p1;
SELECT ##ROWCOUNT;
',N'#p1 int,#p0 bit',#p1=1223424,#p0=1
Find ensures that already loaded entities do not trigger a SELECT and also automatically attaches the entity if needed (from the docs):
Finds an entity with the given primary key values. If an entity with the given primary key values is being tracked by the context, then it is returned immediately without making a request to the database. Otherwise, a query is made to the database for an entity with the given primary key values and this entity, if found, is attached to the context and returned. If no entity is found, then null is returned.
I'm late to the game here, but this is how I am doing it, I spent a while hunting for a solution I was satisified with; this produces an UPDATE statement ONLY for the fields that are changed, as you explicitly define what they are through a "white list" concept which is more secure to prevent web form injection anyway.
An excerpt from my ISession data repository:
public bool Update<T>(T item, params string[] changedPropertyNames) where T
: class, new()
{
_context.Set<T>().Attach(item);
foreach (var propertyName in changedPropertyNames)
{
// If we can't find the property, this line wil throw an exception,
//which is good as we want to know about it
_context.Entry(item).Property(propertyName).IsModified = true;
}
return true;
}
This could be wrapped in a try..catch if you so wished, but I personally like my caller to know about the exceptions in this scenario.
It would be called in something like this fashion (for me, this was via an ASP.NET Web API):
if (!session.Update(franchiseViewModel.Franchise, new[]
{
"Name",
"StartDate"
}))
throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.NotFound));
Entity framework tracks your changes on objects that you queried from database via DbContext. For example if you DbContext instance name is dbContext
public void ChangePassword(int userId, string password){
var user = dbContext.Users.FirstOrDefault(u=>u.UserId == userId);
user.password = password;
dbContext.SaveChanges();
}
I know this is an old thread but I was also looking for a similar solution and decided to go with the solution #Doku-so provided. I'm commenting to answer the question asked by #Imran Rizvi , I followed #Doku-so link that shows a similar implementation. #Imran Rizvi's question was that he was getting an error using the provided solution 'Cannot convert Lambda expression to Type 'Expression> [] ' because it is not a delegate type'. I wanted to offer a small modification I made to #Doku-so's solution that fixes this error in case anyone else comes across this post and decides to use #Doku-so's solution.
The issue is the second argument in the Update method,
public int Update(T entity, Expression<Func<T, object>>[] properties).
To call this method using the syntax provided...
Update(Model, d=>d.Name, d=>d.SecondProperty, d=>d.AndSoOn);
You must add the 'params' keyword in front of the second arugment as so.
public int Update(T entity, params Expression<Func<T, object>>[] properties)
or if you don't want to change the method signature then to call the Update method you need to add the 'new' keyword, specify the size of the array, then finally use the collection object initializer syntax for each property to update as seen below.
Update(Model, new Expression<Func<T, object>>[3] { d=>d.Name }, { d=>d.SecondProperty }, { d=>d.AndSoOn });
In #Doku-so's example he is specifying an array of Expressions so you must pass the properties to update in an array, because of the array you must also specify the size of the array. To avoid this you could also change the expression argument to use IEnumerable instead of an array.
Here is my implementation of #Doku-so's solution.
public int Update<TEntity>(LcmsEntities dataContext, DbEntityEntry<TEntity> entityEntry, params Expression<Func<TEntity, object>>[] properties)
where TEntity: class
{
entityEntry.State = System.Data.Entity.EntityState.Unchanged;
properties.ToList()
.ForEach((property) =>
{
var propertyName = string.Empty;
var bodyExpression = property.Body;
if (bodyExpression.NodeType == ExpressionType.Convert
&& bodyExpression is UnaryExpression)
{
Expression operand = ((UnaryExpression)property.Body).Operand;
propertyName = ((MemberExpression)operand).Member.Name;
}
else
{
propertyName = System.Web.Mvc.ExpressionHelper.GetExpressionText(property);
}
entityEntry.Property(propertyName).IsModified = true;
});
dataContext.Configuration.ValidateOnSaveEnabled = false;
return dataContext.SaveChanges();
}
Usage:
this.Update<Contact>(context, context.Entry(modifiedContact), c => c.Active, c => c.ContactTypeId);
#Doku-so provided a cool approach using generic's, I used the concept to solve my issue but you just can't use #Doku-so's solution as is and in both this post and the linked post no one answered the usage error questions.
Combining several suggestions I propose the following:
async Task<bool> UpdateDbEntryAsync<T>(T entity, params Expression<Func<T, object>>[] properties) where T : class
{
try
{
var entry = db.Entry(entity);
db.Set<T>().Attach(entity);
foreach (var property in properties)
entry.Property(property).IsModified = true;
await db.SaveChangesAsync();
return true;
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("UpdateDbEntryAsync exception: " + ex.Message);
return false;
}
}
called by
UpdateDbEntryAsync(dbc, d => d.Property1);//, d => d.Property2, d => d.Property3, etc. etc.);
Or by
await UpdateDbEntryAsync(dbc, d => d.Property1);
Or by
bool b = UpdateDbEntryAsync(dbc, d => d.Property1).Result;
I use ValueInjecter nuget to inject Binding Model into database Entity using following:
public async Task<IHttpActionResult> Add(CustomBindingModel model)
{
var entity= await db.MyEntities.FindAsync(model.Id);
if (entity== null) return NotFound();
entity.InjectFrom<NoNullsInjection>(model);
await db.SaveChangesAsync();
return Ok();
}
Notice the usage of custom convention that doesn't update Properties if they're null from server.
ValueInjecter v3+
public class NoNullsInjection : LoopInjection
{
protected override void SetValue(object source, object target, PropertyInfo sp, PropertyInfo tp)
{
if (sp.GetValue(source) == null) return;
base.SetValue(source, target, sp, tp);
}
}
Usage:
target.InjectFrom<NoNullsInjection>(source);
Value Injecter V2
Lookup this answer
Caveat
You won't know whether the property is intentionally cleared to null OR it just didn't have any value it. In other words, the property value can only be replaced with another value but not cleared.
_context.Users.UpdateProperty(p => p.Id, request.UserId, new UpdateWrapper<User>()
{
Expression = p => p.FcmId,Value = request.FcmId
});
await _context.SaveChangesAsync(cancellationToken);
Update Property is an extension method
public static void UpdateProperty<T, T2>(this DbSet<T> set, Expression<Func<T, T2>> idExpression,
T2 idValue,
params UpdateWrapper<T>[] updateValues)
where T : class, new()
{
var entity = new T();
var attach = set.Attach(entity);
attach.Property(idExpression).IsModified = false;
attach.Property(idExpression).OriginalValue = idValue;
foreach (var update in updateValues)
{
attach.Property(update.Expression).IsModified = true;
attach.Property(update.Expression).CurrentValue = update.Value;
}
}
And Update Wrapper is a class
public class UpdateWrapper<T>
{
public Expression<Func<T, object>> Expression { get; set; }
public object Value { get; set; }
}
I was looking for same and finally I found the solution
using (CString conn = new CString())
{
USER user = conn.USERs.Find(CMN.CurrentUser.ID);
user.PASSWORD = txtPass.Text;
conn.SaveChanges();
}
believe me it work for me like a charm.
public async Task<bool> UpdateDbEntryAsync(TEntity entity, params Expression<Func<TEntity, object>>[] properties)
{
try
{
this.Context.Set<TEntity>().Attach(entity);
EntityEntry<TEntity> entry = this.Context.Entry(entity);
entry.State = EntityState.Modified;
foreach (var property in properties)
entry.Property(property).IsModified = true;
await this.Context.SaveChangesAsync();
return true;
}
catch (Exception ex)
{
throw ex;
}
}
public void ChangePassword(int userId, string password)
{
var user = new User{ Id = userId, Password = password };
using (var db = new DbContextName())
{
db.Entry(user).State = EntityState.Added;
db.SaveChanges();
}
}