https://github.com/quinntynebrown/effunkiness
Examining the behaviour of the enabling retries and the InvalidOperation Exception when executing two queries on the same context at the same time.
https://github.com/quinntynebrown/effunkiness
aspnetcore efcore5 integration-testing mediatr swagger
Last synced: 7 months ago
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Examining the behaviour of the enabling retries and the InvalidOperation Exception when executing two queries on the same context at the same time.
- Host: GitHub
- URL: https://github.com/quinntynebrown/effunkiness
- Owner: QuinntyneBrown
- Created: 2020-12-16T01:01:13.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2020-12-17T02:03:32.000Z (over 5 years ago)
- Last Synced: 2025-03-17T01:33:33.461Z (about 1 year ago)
- Topics: aspnetcore, efcore5, integration-testing, mediatr, swagger
- Language: C#
- Homepage:
- Size: 33.2 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# EF Funkiness
An example of how you can run into a InvalidOperationException stating that "There is already an open DataReader associated with this Connection which must be closed first." using Entity Framework Core.
## To Run the Api (Swagger)
Using the command line console
1. Navigate to the src\EFFUnkiness.Server folder
2. Execute `dotnet run`
## To Run the Integration tests
Using the command line console
1. Execute `dotnet test`
## Funkiness
The code below will normally throw an InvalidOperationException because while a the underlying DataReader the context is using is open, the Connection is in use exclusively by that DataReader. You cannot execute any commands for the Connection, including creating another DataReader, until the original DataReader is closed.
```csharp
var clients = new List();
var query = from client in _context.Clients
select client;
foreach (var client in query)
{
var user = _context.Users.Single(x => x.UserId == client.CreatedByUserId);
clients.Add(new ClientDto(client.ClientId, client.Name, new UserDto(user.UserId, user.Name)));
}
```
### EnableRetryOnFailure
If you enabled automatic retries (see snippet below), you will not experience any issues.
```csharp
services.AddDbContext(options =>
{
options.UseSqlServer("your-connectionstring",
builder => builder.EnableRetryOnFailure());
});
```
### ToListAsync
You could materialize the query and use ToList(). That would be synchronise and not good. Entity Framework gives you an extension called ToListAsync() that seems to be percisely for this situation. It gives you the streaming behaviour and manages the connections.
```csharp
foreach (var client in await query.ToListAsync())
{
var user = _context.Users.Single(x => x.UserId == client.CreatedByUserId);
clients.Add(new ClientDto(client.ClientId, client.Name, new UserDto(user.UserId, user.Name)));
}
```