I started using Entity Framework 4.3.1 with code first approach.
I want to avoid application crash when database server is shut down or unavailable catching specific exceptions.
Imagine this short sample piece of code:
using (var db = new MyContext())
{
var people = new People();
db.People.AddObject(people);
db.SaveChanges();
}
When server is shut down, I receive ProviderIncompatibleException.
If I try to modify code catching ProviderIncompatibleException like this
using (var db = new MyContext())
{
try
{
var people = new People();
db.People.AddObject(people);
db.SaveChanges();
}
catch(ProviderIncopatibleException)
{
}
}
I receive compiler error "The type caught or thrown must be derived from System.Exception".
How can I catch most specific Exception using Entity framework?
Thank you for help.
There's a typo in the class name - you missed out an 'm' in Incompatible.
Try again with ProviderIncompatibleException
Related
I have following database schema and I would like to seed the data in the database but I could not understand how to seed the images at first go, what should be in the table entity.
I need help to know where I need changes.
Thanks.
Since you referenced Core, here's the easiest way (in Program.Main)
try
{
var host = BuildWebHost(args);
using (var scope = host.Services.CreateScope())
{
var services = scope.ServiceProvider;
try
{
var context = services.GetRequiredService<myContext>();
DbInitializer.Seed(context);
}
catch
{
throw;
}
}
host.Run();
}
catch
{
throw;
}
and create a class called DbInitializer with a method Seed that takes an EF context. I think you can take it from there.
(and don't post images of code, post the code using Ctrl+K to format code-blocks)
I have not had any luck with transactions and entity framework 5. I have the following code:
context.Database.Connection.Open();
transaction = context.Database.Connection.BeginTransaction(IsolationLevel.Serializable);
//some work happens
context.SaveChanges();
//some additional work
context.SaveChanges();
transaction.Commit();
At the very first context.SaveChanges call, I get an exception: "Connection is already part of a local or a distributed transaction"
Right now I am actually just doing a trivial proof of concept where all I am doing is attaching an entity, marking it as modified and then calling save changes.
As a troubleshooting deal, I put in an event handler for when the connection state changes and had a breakpoint in there. Doing that, I verified that the connection did not close on me between when I started the transaction and when I called save changes.
Any help figuring out why it is giving me that exception would be tremendously appreciated.
This is the way we used transactions before. It worked for us:
public void DoSomething()
{
using (var db = GetContext())
{
using (var ts = GetTransactionScope())
{
//do stuff
db.SaveChanges();
ts.Complete();
}
}
}
public TransactionScope GetTransactionScope()
{
var tso = new TransactionOptions { IsolationLevel = IsolationLevel.ReadCommitted };
return new TransactionScope(TransactionScopeOption.Required, tso);
}
If for some reason you have to do multiple SaveChanges calls in one transaction the recommended way is to wrap them in a TransactionScope:
using(var tran = new TransactionScope())
{
using(var context = new MyContext())
{
//some work happens
context.SaveChanges();
//some additional work
context.SaveChanges();
}
tran.Complete(); // without this call the transaction is rolled back.
}
The default isolation level is serializable. Each connection that is opened within the transaction enlists in this transaction. By default, EF always opens and closes connections when it executes queries.
I guess the cause of this exception you've got is that EF creates a transaction object itself when it executes SaveChanges. It tries to use its connection to start this transaction, but the connection is already part of the transaction you created. By using a TransactionScope, the EF transaction just enlists in the ambient transaction.
Can u tell me what is the problem?
If you are using two different instances of the DbContext (the db variable as you named it) then nothing will be saved when you call SaveChanges on a context different than the one where your entities are tracked. You need to use the Attach method first.
db.customer_images.Attach(item);
db.SaveChanges();
However I think in your case you can avoid the attach step if you refactor a bit you code and don't use the DbContext from the entity itself.
Before going through my answer, you must check, if you are attaching the item as shown in excepted answer or check this code:.
if (dbStudentDetails != null && dbStudentDetails.Id != 0)
{
// update scenario
item.Id = dbStudentDetails.Id;
_context.Entry(dbStudentDetails).CurrentValues.SetValues(item);
_context.Entry(dbStudentDetails).State = EntityState.Modified;
}
else
{
// create scenario
_context.StudentDetails.Add(item);
}
await _context.SaveChangesAsync();
If above solution doesn't work, then check the below answer.
Saw a very wired issue, and thought to must answer this. as this can
be a major issue if you have lots of constraints and indexes in your
SQL.
db.SaveChanges() wasn't throwing any error, but not working (I have tried Exception or SqlException). This was not working because the Unique constraint was not defined properly while creating the Entity Models.
How you can Identified the issue:
I connected my SQL Server and opened the SQL Profiler.
Just before the db.SaveChanges(), I cleared all my profiler logs and ran the db.SaveChanges(). It logged the statement. I copied the script from the profiler and ran the script in SQL Server.
And bingo, I can see the actual error, which is being thrown at SQL Server side.
(images: have some hints, how you can get the execute statement from Profiler and run on sql server)
What you can do For Entity Framework Core:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Students>().HasIndex(p => new { p.RollNumber, p.PhoneNumber }).IsUnique(true).IsClustered(false).HasDatabaseName("IX_Students_Numbers");
}
What you can do For Entity Framework 6 and below:
using System.Data.Entity.ModelConfiguration;
internal partial class StudentsConfiguration : EntityTypeConfiguration<Students>
{
public StudentsConfiguration()
{
HasIndex(p => new { p.RollNumber, p.PhoneNumber }).IsUnique(true).IsClustered(false).HasName("IX_Students_Numbers");
}
}
Try to query your entity by Id, eg:
entity = this.repo.GetById(item.id);
entity.is_front = false;
if (dbSaveChanges() > 0)
{
....
}
In my sql stored procedure, i do some insertion and updating which in some scenarios throws Primary Key or unique key violation.
When I try to execute this procedure from ADO.net, .net application also throws that exception and let me know that something wrong had happen.
But when I try to execute this procedure from EF, it just executes. Neither it show anything nor update anything.
How should I handle or notify user that something wrong had happen?
Ado.Net code is
SqlConnection sqlConnection = new SqlConnection(#"data source=database01; database=test; user id=test; password=test;");
SqlCommand cmd = new SqlCommand("[uspUpdateTest]", sqlConnection);
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("RunID", RunID);
cmd.Parameters.AddWithValue("RunCode", RunCode);
sqlConnection.Open();
var str = cmd.ExecuteNonQuery();
Entity Framework Code is
TestEntities context = new TestEntities();
var str=context.UpdateRun(RunID, RunCode);
I am very much sure, you must set some return type(dummy) in your function import. It makes sense most of the time, because if you don't do so, your method name does not appear in intellisense and you will no be able to access it using context.MethodName.
My suggestion for you is, remove the return type of your Function Import and set it to none. Execute your method using ExecuteFunction method of context.
Context.ExecuteFunction(FunctionName,Parameters). It'll definitely throws the exception.
First of all, make sure you're throwing an Exception in your stored procedure which we can catch in our C# code. See - http://social.msdn.microsoft.com/forums/en-US/adodotnetdataproviders/thread/efea444e-6fca-4e29-b100-6f0c5ff64e59 - quote:
If you want RAISERROR to throw a SqlException, you need to set its
severity above 10. Errors with a severity of 10 and below are
informational, and thus don't throw exceptions.
I'll also show you the following code. I have been using this in my MVC controllers when getting data from my service layer using Entity Framework:
try
{
try
{
//Entity Framework/Data operations that could throw the data exception
//...
} catch (DataException dex) //see http://msdn.microsoft.com/en-us/library/system.data.dataexception.aspx
{
//Specifically handle the DataException
//...
}
}
catch (Exception e)
{
//do something (logging?) for the generic exception
throw e;
}
You can put a breakpoint on the last catch if the first catch doesn't trigger to see Exception-type/inner-exception of 'e' and go from there. It is useful to put a breakpoint on the generic exception, as it let's me know when I haven't handled something.
We can use the following way for sql raised error exception from entity framework:
Let's say, we have DBContext. So that
var connection= (SqlConnection)db.Database.Connection;
if (connection != null && connection.State == ConnectionState.Closed)
{
connection.Open();
}
SqlCommand com = new SqlCommand("spname", connection);
com.CommandType = CommandType.StoredProcedure;
com.Parameters.Add(new SqlParameter("#parameter", parameter));
try
{
com.ExecuteNonQuery();
}
catch (Exception ex)
{
throw ex.message;
} `
The question here gives quite a nice summary of catching and handling the exceptions gracefully. You have several options after that for rolling back etc.
I have created a sample application in Silverlight with RIA services. I am using entity framework for CRUD operation but it does not work for INSERT Operation with following Exception, "Submit operation failed validation. Please inspect Entity.ValidationErrors for each entity in EntitiesInError for more information." I have not apply any validation but don't know how the error occurs.
I have tested that when I create an object of DB entity and assign values to it and then save by calling object.SaveChages(), it works fine. But its default method does not work. Any help is appreciated.
Thanks
The SubmitOperation callback has an EntitiesInError property which you can use to iterate thru the entities. That's the way of getting the "real" error.
Here's the method I have to show the user what went wrong...
public static bool WasSubmittedOK(SubmitOperation so, string errorMessageHeader, out string errorMessage)
{
errorMessage = string.Empty;
if (!so.HasError)
return true;
so.MarkErrorAsHandled();
errorMessage = "An unknown error has occurred";
if (so.EntitiesInError.Count() > 0)
{
StringBuilder builder = new StringBuilder();
builder.AppendFormat("{0}\r\n", errorMessageHeader);
foreach (Entity item in so.EntitiesInError)
{
#if DEBUG
builder.AppendFormat("\r\nFor {0}", item.GetType());
#endif
foreach (ValidationResult error in item.ValidationErrors)
{
builder.AppendFormat("\r\n- {0}", error.ErrorMessage);
Debug.WriteLine(string.Format("Error in {0}:'{1}'", string.Join(",", error.MemberNames.ToArray()), error.ErrorMessage));
}
}
errorMessage = builder.ToString();
}
else if (so.Error != null) { errorMessage = so.Error.Message; }
return false;
}
Are you able to drill into the validation errors? I actually have an article about this coming in December MSDN Magazine Data Points but I bet you don't want to wait, right? :)
Even if you haven't applied any specific validations, there are things like foreign key contsraints that EF will still check. If you can see what the error is that will be ultimately useful in solving your problem. Debug into the exception. See if there is a DbEntityValidationException available...maybe it's in an innerexceptoin. DbEntityValidationException will have one or more EntityValidationErrors. Each of those contains a list of all of the errors found for one instance. That means expanding the EntityValidationErrors items one at a time and looking at the ValidationError items contained within.