how to debug dotnet ef database drop?




On Running `dotnet ef database drop` I get an error. How can I debug this command, to get more details about the problem? Or how can I find the source of this error?



> 
> System.ObjectDisposedException: Cannot access a disposed object. A common cause of this error is disposing a context that was resolved from dependency injection and then later trying to use the same context instance elsewhere in your application. This may occur if you are calling Dispose() on the context, or wrapping the context in a using statement. If you are using dependency injection, you should let the dependency injection container take care of disposing context instances.
>  Objektname: "ApplicationDbContext".
>  bei Microsoft.EntityFrameworkCore.DbContext.get\_InternalServiceProvider()
>  bei Microsoft.EntityFrameworkCore.DbContext.Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure.get\_Instance()
>  bei Microsoft.EntityFrameworkCore.Infrastructure.AccessorExtensions.GetService[TService](IInfrastructure`1 accessor)
>  bei Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
>  bei Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
>  bei Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.DropDatabase(String contextType)
>  bei Microsoft.EntityFrameworkCore.Design.OperationExecutor.DropDatabaseImpl(String contextType)
>  bei Microsoft.EntityFrameworkCore.Design.OperationExecutor.DropDatabase.<>c\_\_DisplayClass0\_1.<.ctor>b\_\_0()
>  bei Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
>  Cannot access a disposed object. A common cause of this error is disposing a context that was resolved from dependency injection and then later trying to use the same context instance elsewhere in your application. This may occur if you are calling Dispose() on the context, or wrapping the context in a using statement. If you are using dependency injection, you should let the dependency injection container take care of disposing context instances.
>  Objektname: "ApplicationDbContext".
> 
> 
>
I have the same problem and added this to the DbContext:



```
private void PrintStackTrace()
{
  var st = new StackTrace();
  foreach (var sf in st.GetFrames())
    Console.WriteLine($"{sf.GetMethod().DeclaringType.Assembly.GetName().Name} {sf.GetMethod().DeclaringType.Name} {sf.GetMethod().Name}");
}

```

and call this function in the contructor and Dispose of the DbContext.


It seems to be a problem, if the DbContext is added with scoped lifetime to the dependency injection. I filed an issue for that.


<https://github.com/aspnet/EntityFrameworkCore/issues/10693>
hi [@gianna.demetroulakos](/u/gianna.demetroulakos),

as mentioned by [@william.coulson](/u/william.coulson), the object reference not set to an instance of an object normally occurs when a variable is null.

run the code in the debug mode.

when the error occurs, check the variable which has a null value in locals tab.

warm regards,

ranjith u… A couple of notes to get started:



> 
> .apply(literal\_eval)
> 
> 
> 


Wouldn't this be better as `map`?



> 
> I then re-create the Dask DF:
> 
> 
> ddf = dd.from\_pandas(ddf\_out, npartitions=nCores)
> 
> 
> 


`ddf_out` was already a dask dataframe, I don't know why you had to do this.



> 
> The columns in result seem to match those in metadir.
> 
> 
> 


The value of `result.columns` is taken from the meta you provided, no computing happens until you ask for it (dask is lazy in most operations). Does the ValueError exception not provide further information?


Here is a full example



```
x = ({'F9_07_PZ_COMP_DIRECT': '0',
  'F9_07_PZ_DIRTRSTKEY_NAME': 'DEBRA MEALY',
  'F9_07_PZ_COMP_OTHER': '0',
  'F9_07_PZ_COMP_RELATED': '0',
  'F9_07_PZ_TITLE': 'CHAIR PERSON',
  'F9_07_PZ_AVE_HOURS_WEEK': '1.00',
  'F9_07_PC_TRUSTEE_INDIVIDUAL': 'X'},
 {'F9_07_PZ_COMP_DIRECT': '0',
  'F9_07_PZ_DIRTRSTKEY_NAME': 'HELEN GORDON',
  'F9_07_PZ_COMP_OTHER': '0',
  'F9_07_PZ_COMP_RELATED': '0',
  'F9_07_PZ_TITLE': 'VICE CHAIR',
  'F9_07_PZ_AVE_HOURS_WEEK': '1.00',
  'F9_07_PC_TRUSTEE_INDIVIDUAL': 'X'})
df = pd.DataFrame({'a': x})
d = dd.from_pandas(df, 1)
meta = pd.DataFrame(columns=['F9_07_PZ_COMP_DIRECT', 
       'F9_07_PZ_DIRTRSTKEY_NAME',
       'F9_07_PZ_COMP_OTHER', 'F9_07_PZ_COMP_RELATED', 'F9_07_PZ_TITLE',
       'F9_07_PZ_AVE_HOURS_WEEK', 'F9_07_PC_TRUSTEE_INDIVIDUAL'], dtype="O")
d.map_partitions(lambda df: df.a.apply(pd.Series), meta=meta).compute()

```

How did I know what `meta` to use? I applied the function to the pandas dataframe - you might use a small piece of the dataframe to do this.


Some additional notes:


* it is an anti-pattern to load the data with pandas, pass to dask workers and then gather the whole result back to a pandas (in memory) dataframe, you are very unlikely to see a speedup this way and may incur a lot of overhead. You are better off loading with something like `dd.read_csv`, and aggregating or writing with dask functions too. Only `compute()` on something that will be small or not return anything (because it involves writing the output). The official examples do not use from\_pandas.
* string and dict processing are python methods, and so hold the interpreter lock (GIL) of any python function: threads will not actually run in parallel. To get parallelism, you need to run in processes, which is most easily achieved using <https://docs.dask.org/en/latest/setup/single-distributed.html>
* the distributed scheduler also gives you access to the dashboard, which has a lot of useful information to diagnose how your system is running. You can also configure a lot about its behaviour, in case you have firewall rules you need to obey. The documentation for [`ConfigurationManager.RefreshSection`](https://docs.microsoft.com/en-us/dotnet/api/system.configuration.configurationmanager.refreshsection?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DEN-US%26k%3Dk(System.Configuration.ConfigurationManager.RefreshSection);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.6.2);k(DevLang-csharp)%26rd%3Dtrue&view=netframework-4.7.2) method does say (emphasis is mine):



> 
> Refreshes the named section **so the next time that it is retrieved** it will be re-read from disk.
> 
> 
> 


The problem is that EF6 caches the [`ConfigurationManager.ConnectionStrings`](https://docs.microsoft.com/en-us/dotnet/api/system.configuration.configurationmanager.connectionstrings?view=netframework-4.7.2) in an internal class static property, so it never gets refreshed.


Unfortunately there is no "official" way to refresh it. Following is a brute force hack using reflection, so use it on your own risk:



```
static readonly Type EF6AppConfigType = typeof(DbContext).Assembly.GetType("System.Data.Entity.Internal.AppConfig");

static readonly PropertyInfo EF6DefaultAppConfig = EF6AppConfigType.GetProperty("DefaultInstance", BindingFlags.Public | BindingFlags.Static);

static readonly FieldInfo EF6ConnectionStrings = EF6AppConfigType.GetField("_connectionStrings", BindingFlags.NonPublic | BindingFlags.Instance);

static void RefreshEF6ConnectionStrings()
{
    EF6ConnectionStrings.SetValue(
        EF6DefaultAppConfig.GetValue(null),
        ConfigurationManager.ConnectionStrings
    );
}

```

Just call it after saving the changes:



```
config.Save();
RefreshEF6ConnectionStrings();

``` Hello Dmytro,


You will need to bind to the Custom Command, create arguments for the command execution, specify parameter values that will be used to execute the command in the Scheduled Task and then pass the arguments to the Arguments property of the action. Here is the code that will do the trick:



```
# Define actions and conditions for the task

$commandID = "{a7264a61-b77d-4386-a138-ec2557c5b3ba}" # Command ID
$commandDN = "CN=MyCommand,CN=Custom Commands,CN=Configuration Objects,CN=Adaxes Configuration,CN=Adaxes" # Command DN

# Create action set
$actionsAndConditions = $task.ConditionedActions.Create()
$actionsAndConditions.ConditionsLogicalOperation = "ADM_LOGICALOPERATION_AND"
$actionsAndConditions.SetInfo()

# Create execute Custom Command action
$action = $actionsAndConditions.Actions.CreateEx("adm-CustomCommandAction")
$action.ExecutionOptions = "ADM_ACTIONEXECUTIONOPTIONS_SYNC"

# Get action
$removeAction = $action.GetAction()

# Bind to Custom Command
$customCommand = $Context.BindToObjectByDN($commandDN)

# Specify command arguments
$arguments = $customCommand.CreateArguments()
$arguments.SetParameterValue("MyParameter", "MyValue") # Parameter value

# Configure the action
$removeAction.CustomCommandId = $commandID
$removeAction.Arguments = $arguments

# Save action
$action.SetAction($removeAction)
$action.SetInfo()
```

In the script, the $commandDN variable specifies the distinguished name (DN) of the Custom Command. For information on how to get the DN of a directory object, see <http://adaxes.com/sdk/?HowDoI.GetDnOfObject.html>.


For details, have a look at the following SDK article: <http://adaxes.com/sdk/?IAdmCustomCommandAction2.html>. > You might have missed a bracket somewhere... Only such a mistake causes so many insignificant errors.
> 
> 


And to find it, [format your code](http://www.gidnetwork.com/b-38.html) properly. It's your first debugging tool. The object you are linking with was built with the option to use the static run-time libraries, whereas your DLL was (properly) built to use the DLL libraries. When you mix these you'll get complaints such as this.


Since Fortran objects don't care which library set is used (this is not true of C/C++), one option could be to set the Linker>Input property "Ignore all default libraries" (/NODEFAULTLIB) in your DLL project. You will then need to name the required libraries under Additional Dependencies. (You can use the dumpbin command on your DLL's object to see a list.)


If you can rebuild the external object, do so with the Fortran > Libraries > Disable default library search rules property set to Yes. Then you should be able to link it in without further issue.




[View solution in original post](/t5/Intel-Fortran-Compiler/Error-linking-to-external-obj-file/m-p/1144075#M138021) Try using VS's deployment tools next time as creating a folder and dropping exe's in there can be trouble as in permissions, ownership etc. A few things to try.


1. Use [Variable Tables](http://odetocode.com/Articles/365.aspx) instead -> maybe the import wizard prefers that?
2. Name your return fields.


Try using the following stored proc (untested .. just thinking out loud...)



```
CREATE PROCEDURE dbo.Foo
AS

    SET NOCOUNT ON

    DECLARE @ResultTable TABLE (SomeId INTEGER)

    INSERT INTO @ResultTable
    SELECT DISTINCT Id AS Identity -- Or u can rename this field to anything...
    FROM SomeExistingTableWhichHasAnIdentityField

GO

```

Try that and see if the wizard refreshes, now.


-- 


 Attempt #2 :)


Ok .. when the EF designer/wizard/whatever fails to figure out EXACTLY what my stored proc is suppose to be returning, I usually do the following :-


1. Make sure the stored procedure doesn't exist at all in the EF designer/context, etc. (You have a clean starting point)
2. Open up your stored procedure and `/* /*` comment out *EVERYTHING* after the procedure definition.


eg..



```
ALTER PROCEDURE dbo.Foo
(
    Bar1 INT,
    Bar2 TINYINT,
    ... // whatever u have as your optional input arguments //
)
AS
    SET NOCOUNT ON

    /* 
    .... every thing in here is commented out 
    */
GO

```

Now ...
 3. Add a forced fake return in the stored proc, which (more or less) just *defines* the output structure/fields.


eg..



```
ALTER PROCEDURE dbo.Foo
(
    Bar1 INT,
    Bar2 TINYINT,
    ... // whatever u have as your optional input arguments //
)
AS
    SET NOCOUNT ON

    SELECT 1 AS Id, 1 AS UserId, 1 AS SomeOtherId, 
        CAST('AAA' AS NVARCHAR(350)) AS Name,
        -- etc etc etc..
    /* 
    .... every thing in here is commented out 
    */
GO

```

[and then](http://www.youtube.com/watch?v=K7luMp6lb9M) ...


4. Add this stored proc to your EF designer/wizard/etc... Now the correct fields should be 'determined' by the designer. AWESOME. Yes .. the values are all hardcoded .. but that's ok (so far).
5. Once your happy that EF is now updated right, go back to your stored proc, and remove all hardcoded SELECT (which we did in the above step). Now we remove the comments which we commented out the entire real code. So you should have your original stored proc, back.


... and now EF is updated and doesn't know we've changed the plumbing of your stored proc.


win :)


does this work for ya? [image] dueck456:

is there an easy way to detect when new code is flashed to the device so i can reinitialize the retained variables?

below is a link to a post by [@rickkas7](/u/rickkas7) about storing retained data in a struct.

[image] dueck456:

saving a know value to eeprom jumps to mind

there is … If I am not wrong, you are trying to read or loop through the rows from datatable. This error states that the datasource(DataTable) is not having any rows. To avoid this exception use this before you read or loop through datatable:  


```
if(dt.Rows.Count  > 0 ){
     //Do your stuff here.
}
```
  

  

  

--Amit