I have a working ASP.NET Web API that I am trying to convert to ASP.NET Core. I am struggling with a multi-table item add. I have the following 4 tables (SQL Server):
Template,
TemplateAction - with a foreign key to Template,
TemplateGroup - with a foreign key to Template,
TemplateCell - with a foreign key to Template, a foreign key to TemplateAction and a foreign key to TemplateGroup.
The code to add the "Template" (with one TemplateAction, one TemplateGroup and one TemplateCell) is as follows:
public async Task<int> CreateTemplate(string userId, TemplateCreateDTO dto)
{
using (var context = MyDataContext.Instance) // Injected in ASP.NET Core (no using)
{
var now = DateTime.UtcNow;
// Create s single default Group
var groups = new[]
{
new TemplateGroup
{
Name = "Row Name",
Description = string.Empty,
SortOrder = 0
}
};
// Create s single default Action
var actions = new[]
{
new TemplateAction
{
Name = "Column Name",
Description = string.Empty,
SortOrder = 0
}
};
// All cells are enabled when a Template is created
var cells = new[]
{
new TemplateCell
{
TemplateGroupId = groups[0].Id,
TemplateActionId = actions[0].Id,
IsEnabled = true
}
};
var template = new Template
{
Name = dto.Name,
Description = dto.Description,
InitialRisk = dto.InitialRisk,
CreatedWhen = now,
CreatedByUserId = userId,
ModifiedWhen = now,
ModifiedByUserId = userId,
TemplateGroups = groups,
TemplateActions = actions,
TemplateCells = cells
};
context.Templates
.Add(template);
await context.SaveChangesAsync();
return template.Id;
}
}
The same code in ASP.NET Core 3.1 (EF Core 3.1) - apart from the context is injected - fails with the following error:
The INSERT statement conflicted with the FOREIGN KEY constraint \"FK_TemplateCell_TemplateAction\". The conflict occurred in database \"MyDB\", table \"dbo.TemplateAction\", column 'Id'.\r\nThe statement has been terminated.
I have tried numerous things, but have been unable to add the template. Can anyone see what the issue may be? Thanks.
var cells = new[]
{
new TemplateCell
{
TemplateGroupId = groups[0].Id,
TemplateActionId = actions[0].Id,
IsEnabled = true
}
};
the ids will have no value when you try to save..
I guess you have to do something like this
var cells = new[]
{
new TemplateCell
{
TemplateGroup = groups[0],
TemplateAction = actions[0],
IsEnabled = true
}
};
when the referenced object is saved it will set the fk to you..
anyway, you see that to ensure that your group / action / cell point to same template you should use a composite primary key if you realy want that all have a fk to the template, right?
or is expected that they can reference different templates?
How to pass data from a method to another inside a controller and display.
The first method have list of values and this has to pass to the another and display that data from the view
first action method:
[HttpPost]
public ActionResult matchpin(string id)
{
int d = Convert.ToInt32(id);
List<pin> plist = new List<pin>();
using (SqlConnection con = new SqlConnection(constring))
{
using (SqlCommand cmd = new SqlCommand("getpin", con))
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("#pin", d);
con.Open();
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
var pin = new pin()
{
// Vid=Convert.ToInt32(reader["Vid"]),
po = Convert.ToString(reader["po"]),
};
plist.Add(pin);
}
}
}
return RedirectToAction("Index","home",new{ s =plist});
}
second action method:
public ActionResult Index(List<pin> plist)
{
// return View();
ViewBag.s = plist;
return View("Index");
//return new ContentResult { Content =TempData["Data"].ToString() };
}
redirect in the first action method has to be
return RedirectToAction("Index","home",new{plist});
instead of
return RedirectToAction("Index","home",new{s=plist});
because ASP MVC framework match it by method parameter name so you have to pass it with the same name in the action method two which is plist.
Using action you can pass limited data.
Mvc provides tempdata to pass data from one action to another.
You can also using session for storing data.
e. g
For passing data:
TempData["mydata"] =myList;
For data retrieval :
var data=TempData["mydata"] ;
Hope that clarify you question.
Using action you can pass limited data.
Mvc provides TempData to pass data from one action to another.
You can also using session for storing data.
e.g
For storing data:
TempData["mydata"]=data;
For retrieving :
var storedData=TempData["mydata"]
You can use TempData: first store your value in TempData, and then redirectToAction:
TempData.MyList=plist;
return RedirectToAction("Index","home");
Problem
I want my Ajax form to pass the value of the selected DropDownListFor to the controller but I can't figure out why the controller is not taking any value.
I am working with ASP.NET MVC and I would like to stick with the helper functions as much as I can.
View
#using (Ajax.BeginForm(new AjaxOptions {
HttpMethod = "Get",
UpdateTargetId = "UserResults",
InsertionMode = System.Web.Mvc.Ajax.InsertionMode.Replace }))
{
#Html.DropDownListFor(Model => Model.Roles, new SelectLi(ViewBag.Groups
as System.Collections.IEnumerable, "Value", "Text"), "Select a group",
new { id = "Value", onchange = "$(this.form).submit();" })
}
#Html.Partial("_UsersGroup", ViewData)
Controller
public ActionResult test(int? selectGroup)
{
// Generate dropdownlist Groups
List<SelectListItem> groupList = new List<SelectListItem>();
var query = from s in db.Roles select s;
if (query.Count() > 0)
{
foreach (var v in query)
{
groupList.Add(new SelectListItem { Text = v.Name, Value =
v.ID.ToString() });
}
}
ViewBag.Groups = groupList;
// End
// This part is supposed to take the passed value as parameter
if (selectGroup == null)
{
// To do code comes here, which takes selectGroup as parameter
}
Details
The form should pass a value based on the selection to the controller which takes it as "selectGroup".
ps. this is my first time asking a question, I'm sorry if I made mistakes.
The parameter of you method needs to match the name of the control which is name="Roles" so the method should be
public ActionResult test(int? roles)
Other potential issues with your code
Your controller generates List<SelectListItem> for use by the dropdownlist. There is no need for the unnecessary extra overhead of then creating a new SelectList (which is IEnumerable<SelectListItem>) from it. The view code can simply be #Html.DropDownListFor(m => m.Roles, (IEnumerable<SelectListItem>)ViewBag.Groups, "Select a group")
Do not use Model (capital M) in the expression. If you make any other reference to the model in your view (e.g. #Model.SomeProperty) you will get an error. Using lower case model => model.somProperty is OK but you can simply use m => m.someProperty
The helper will generate an id attribute (in you case id="Role") so it seems unclear why you are adding new { id = "Value", ..}, especially since you don't appear to be referencing the element by its id anywhere
Learn to use Unobtrusive Javascript rather than polluting you mark up with behavior. Remove the onclick attribute and use $('#Roles').change(function() { $('form').submit(); });
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();
}
}