Alright, let's dig into this frustrating issue—code that worked perfectly fine suddenly throwing exceptions when trying to create a D3D11 device. First, let's look at the relevant code snippet properly formatted:

HRESULT DC11::TryCreateDevice( _In_ IDXGIAdapter* pAdapter, D3D_DRIVER_TYPE driverType, UINT createDeviceFlags, _COM_Outptr_ ID3D11Device** ppDevice, _Out_opt_ UINT* pShaderModel, _COM_Outptr_ ID3D11DeviceContext** ppDeviceContext) { 
    UINT createDeviceFlags0 = 0; 
#ifdef _DEBUG 
    createDeviceFlags0 = D3D11_CREATE_DEVICE_DEBUG; 
#endif 
    if ((createDeviceFlags & ...) // Your truncated logic here

Based on my experience with D3D11, here are the most likely culprits and actionable steps to fix this:

Common Causes & Fixes #

1. Driver/System Update Breakage #

If this started happening out of nowhere, the #1 suspect is a recent graphics driver update or Windows update. D3D11 can be finicky with driver changes—sometimes new drivers tighten validation on device creation flags or remove support for older feature levels.

What to do:

• Roll back your graphics driver to the version that was working when the code functioned correctly.
• Check Windows Update for any pending optional updates related to DirectX or graphics components.
• Verify that your target DirectX runtime (D3D11) is still properly installed (though Windows usually handles this, corrupted runtimes can cause issues).

2. Conflicting Device Creation Flags #

Your code combines createDeviceFlags (passed in) with createDeviceFlags0 (DEBUG-mode debug flag). It's possible the combined flags now include incompatible options that the driver no longer tolerates.

What to do:

• Simplify the flags first: comment out the createDeviceFlags0 line temporarily and try creating the device with just the passed-in createDeviceFlags. If that works, the debug flag might be conflicting with other flags in your build.
• Check for invalid flag combinations: For example, D3D11_CREATE_DEVICE_DEBUG shouldn't be used with D3D11_CREATE_DEVICE_SINGLETHREADED in some scenarios, or certain flags might not be supported on your current GPU.
• Print the combined flag value in debug mode to see exactly what's being passed to D3D11CreateDevice.

3. Invalid/Unavailable Adapter (pAdapter) #

If the pAdapter pointer is pointing to an adapter that's no longer available (e.g., user switched GPUs, virtual GPU in a VM crashed, or hardware failure), device creation will fail.

What to do:

• Before calling TryCreateDevice, validate that pAdapter is not null and that you can still enumerate it via IDXGIFactory::EnumAdapters.
• Try passing nullptr instead of pAdapter to let D3D11 pick the default adapter—if this works, your original adapter is the problem.

4. Feature Level/Shader Model Mismatch #

The pShaderModel output suggests your code is setting a target shader model based on the device's feature level. If your feature level array is missing a level supported by the current GPU, or is ordered incorrectly, device creation can fail.

What to do:

• Ensure your feature level list is ordered from highest to lowest (D3D11 expects this). A standard list looks like:

  D3D_FEATURE_LEVEL featureLevels[] = {
      D3D_FEATURE_LEVEL_11_1, D3D_FEATURE_LEVEL_11_0,
      D3D_FEATURE_LEVEL_10_1, D3D_FEATURE_LEVEL_10_0,
      D3D_FEATURE_LEVEL_9_3, D3D_FEATURE_LEVEL_9_2, D3D_FEATURE_LEVEL_9_1
  };
  

• After device creation, check the selected feature level to confirm it matches what your shader model logic expects.

5. Hidden Resource Leaks #

If previous device/context instances weren't properly released (reference counts not decremented to zero), creating a new device can hit resource limits and throw exceptions.

What to do:

• Use the D3D11 Debug Layer (enabled via D3D11_CREATE_DEVICE_DEBUG) to check for leaks. It will output detailed warnings about unreleased resources in the debug console.
• Ensure all ID3D11Device, ID3D11DeviceContext, and related COM objects are properly released with Release() when no longer needed.

Debugging Pro Tip #

Always capture the exact HRESULT returned by D3D11CreateDevice—this is your most valuable clue. Convert it to a readable string using DXGetErrorStringA or FormatMessage to get specific details about why creation failed. For example:

HRESULT hr = D3D11CreateDevice(...);
if (FAILED(hr)) {
    char errorBuf[512];
    DXGetErrorStringA(hr, errorBuf, sizeof(errorBuf));
    OutputDebugStringA("Device creation failed: ");
    OutputDebugStringA(errorBuf);
    OutputDebugStringA("\n");
    return hr;
}

内容的提问来源于stack exchange，提问作者MNagy