> For the complete documentation index, see [llms.txt](https://docs.gapvelocity.ai/webmap/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.gapvelocity.ai/webmap/general/backend/faq/untitled-5.md).

# What is the Mobilize.Extensions.Logging.RollingFile?

This is a Nuget Package that when added to the migration Solutions enable a Logger Provider for `ASP.Net Core`. This logger provider lets the user adds all logs into files, what can be useful for user to understand the application execution or for determining the reason of an error.

## Using the Rolling File Provider <a href="#using-the-rolling-file-provider" id="using-the-rolling-file-provider"></a>

Configure the provider by calling `AddFile()` on an `ILoggingBuilder` during logger configuration in *Program.cs*.

```
public class Program
{
    public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureLogging(builder => builder.AddFile()) // <- Add this line
            .UseStartup()
            .Build();
}
```

You can pass additional options to the Add File by passing an `Action`, for example:

```
public class Program
{
    public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureLogging(builder => builder.AddFile(options => {
                options.FileName = "diagnostics-"; // The log file prefixes
                options.LogDirectory = "LogFiles"; // The directory to write the logs
                options.FileSizeLimit = 20 * 1024 * 1024; // The maximum log file size (20MB here)
            })) 
            .UseStartup()
            .Build();
}
```

**Finally,** The provider will create log files prefixed with the `FileName`, and suffixed with the current date in the `yyyyMMdd` format.

```
log-20160631.txt
log-20160701.txt
log-20160702.txt
```

Logs will look something like the following:

```
2017-09-01 18:34:18.083 +01:00 [Information] Microsoft.AspNetCore.Hosting.Internal.WebHost: Request starting HTTP/1.1 GET http://localhost:50037/api/values  
2017-09-01 18:34:18.159 +01:00 [Information] Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker: Executing action method SampleApp.Controllers.ValuesController.Get (SampleApp) with arguments ((null)) - ModelState is Valid
2017-09-01 18:34:18.161 +01:00 [Information] SampleApp.Controllers.ValuesController: Executed Get action
2017-09-01 18:34:18.165 +01:00 [Information] Microsoft.AspNetCore.Mvc.Internal.ObjectResultExecutor: Executing ObjectResult, writing value Microsoft.AspNetCore.Mvc.ControllerContext.
2017-09-01 18:34:18.192 +01:00 [Information] Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker: Executed action SampleApp.Controllers.ValuesController.Get (SampleApp) in 36.3435ms
2017-09-01 18:34:18.195 +01:00 [Information] Microsoft.AspNetCore.Hosting.Internal.WebHost: Request finished in 113.6076ms 200 application/json; charset=utf-8
```