ASP.NET Core Configuration Issue with In Process Hosting

Since ASP.NET Core 2.2 was released I have been working on getting all my different applications updated and using in-process hosting. I pretty quickly hit an issue with an application that uses SQLite. As soon as the application tried to access the database I ended up with the following error.

SqliteException: SQLite Error 14: ‘unable to open database file’. Microsoft.Data.Sqlite.SqliteException.ThrowExceptionForRC(int rc, sqlite3 db) Microsoft.Data.Sqlite.SqliteConnection.Open() Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnection(bool errorsExpected)

Issue

After some Googling, I found an issue on GitHub that details the problem. It turns out that when the application gets its current directory it is returning the path to the IIS process that is hosting the application instead of the directory when the application is.

Work Around

On another GitHub issue, I found a link to a recommended workaround. Add the following class somewhere in your application. This code comes here.

internal class CurrentDirectoryHelpers
{
    internal const string AspNetCoreModuleDll = "aspnetcorev2_inprocess.dll";

    [System.Runtime.InteropServices.DllImport("kernel32.dll")]
    private static extern IntPtr GetModuleHandle(string lpModuleName);

    [System.Runtime.InteropServices.DllImport(AspNetCoreModuleDll)]
    private static extern int http_get_application_properties(ref IISConfigurationData iiConfigData);

    [System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)]
    private struct IISConfigurationData
    {
        public IntPtr pNativeApplication;
        [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.BStr)]
        public string pwzFullApplicationPath;
        [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.BStr)]
        public string pwzVirtualApplicationPath;
        public bool fWindowsAuthEnabled;
        public bool fBasicAuthEnabled;
        public bool fAnonymousAuthEnable;
    }

    public static void SetCurrentDirectory()
    {
        try
        {
            // Check if physical path was provided by ANCM
            var sitePhysicalPath = Environment.GetEnvironmentVariable("ASPNETCORE_IIS_PHYSICAL_PATH");
            if (string.IsNullOrEmpty(sitePhysicalPath))
            {
                // Skip if not running ANCM InProcess
                if (GetModuleHandle(AspNetCoreModuleDll) == IntPtr.Zero)
                {
                    return;
                }

                IISConfigurationData configurationData = default(IISConfigurationData);
                if (http_get_application_properties(ref configurationData) != 0)
                {
                    return;
                }

                sitePhysicalPath = configurationData.pwzFullApplicationPath;
            }

            Environment.CurrentDirectory = sitePhysicalPath;
        }
        catch
        {
            // ignore
        }
    }
}

Finally, in the Main function of the Program class add the following line as the first thing in the function.

CurrentDirectoryHelpers.SetCurrentDirectory();

Wrapping Up

With the above changes, all will work as expected. It is my understanding that this issue will be addressed at some point in the future as a patch so this should just be a temporary fix.


Also published on Medium.

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