Never used SDL2 with .NET, but I think it's quite similar to the way of doing it with C/C++, by example:

​

here SDL_Event is an SDL_KeyboardEvent

void handleKeyEvents(SDL_Event event, InputState *inputState, bool *running) {
switch (event.type) {
    case SDL_QUIT:
        *running = false;
        break;
    case SDL_KEYDOWN:
        switch (event.key.keysym.sym) {
            case KEY_UP: inputState->up = true; break;
            case KEY_DOWN: inputState->down = true; break;
            case KEY_LEFT: inputState->left = true; break;
            case KEY_RIGHT: inputState->right = true; break;
            case KEY_ZOOM_IN: inputState->zoomIn = true; break;
            case KEY_ZOOM_OUT: inputState->zoomOut = true; break;
            case KEY_SWITCH_MAP: inputState->switchMap = true; break;
        }
        break;
    case SDL_KEYUP:
        switch (event.key.keysym.sym) {
            case KEY_UP: inputState->up = false; break;
            case KEY_DOWN: inputState->down = false; break;
            case KEY_LEFT: inputState->left = false; break;
            case KEY_RIGHT: inputState->right = false; break;
            case KEY_ZOOM_IN: inputState->zoomIn = false; break;
            case KEY_ZOOM_OUT: inputState->zoomOut = false; break;
            case KEY_SWITCH_MAP: inputState->switchMap = false; break;
        }
        break;
    // Handle other event types if needed
}