Using C#, .NET 9 and I have added the nuget package for System.Data.Oledb

I have included using System.Data.Oledb

The file System.Data.Oledb.dll is in the same folder as the exe.

When I launch the exe in debug mode (debugger attached) everything works.

When I launch the same exe without debugger I get the error

Could not load file or assembly 'System.Data.OleDb, Version=9.0.0.3, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The system cannot find the file specified.

Why can't it find the assembly without debugger attached?

Note: I'm running in EXCATLY the same location - just with the debugger or without the debugger.

Using C#, .NET 9 and I have added the nuget package for System.Data.Oledb

I have included using System.Data.Oledb

The file System.Data.Oledb.dll is in the same folder as the exe.

When I launch the exe in debug mode (debugger attached) everything works.

When I launch the same exe without debugger I get the error

Could not load file or assembly 'System.Data.OleDb, Version=9.0.0.3, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The system cannot find the file specified.

Why can't it find the assembly without debugger attached?

Note: I'm running in EXCATLY the same location - just with the debugger or without the debugger.

• c#
• -core
• -assembly

• Did you ensure that System.Data.OleDb.dll is copied to the output directory? If yes, then If your app is not running in a development environment, dependencies may be missing on the target machine. Considering your answer I may figure it out. – Emad Kerhily Commented Mar 13 at 23:51
• @EmadKerhily I've updated my question to make it clear I'm launching the app from the same location each time. – Michael T Commented Mar 13 at 23:57
• Let's try my answer and test some solutions step by step – Emad Kerhily Commented Mar 14 at 0:10
• 1 @EmadKerhily Thanks your answer explicitly loading the assembly at runtime combined with this stackoverflow/questions/79164448/… helped me figure it out. The build process now copies the specific files from the runtimes subfolder. But I have no idea why it worked under debug mode. – Michael T Commented Mar 14 at 1:07
• Because, when you run in debug mode, Visual Studio ensures dependencies are loaded – Emad Kerhily Commented Mar 14 at 1:20

1 Answer 1

Even though you have System.Data.OleDb.dll in the same folder, it’s worth ensuring it's copied correctly during build.

Modify your .csproj file to always copy the DLL to the output:

<ItemGroup>
    <None Update="System.Data.OleDb.dll">
        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
</ItemGroup>

clean and rebuild the project and let me know if it works.

Alternatively, you can load assembly at runtime explicitly in your program.cs:

AppDomain.CurrentDomain.AssemblyResolve += (sender, args) =>
{
    if (args.Name.Contains("System.Data.OleDb"))
    {
        string path = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "System.Data.OleDb.dll");
        return File.Exists(path) ? Assembly.LoadFrom(path) : null;
    }
    return null;
};