internal static extern ulong VR_IVRSystem_GetUint64TrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, TrackedDeviceProperty prop, ref TrackedPropertyError pError);

 internal static extern HmdMatrix34_t VR_IVRSystem_GetMatrix34TrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, TrackedDeviceProperty prop, ref TrackedPropertyError pError);

 internal static extern uint VR_IVRSystem_GetStringTrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, TrackedDeviceProperty prop, System.Text.StringBuilder pchValue, uint unBufferSize, ref TrackedPropertyError pError);

 public abstract ulong GetUint64TrackedDeviceProperty(uint unDeviceIndex,TrackedDeviceProperty prop,ref TrackedPropertyError pError);

 internal static extern float VR_IVRSystem_GetFloatTrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, TrackedDeviceProperty prop, ref TrackedPropertyError pError);

 public abstract HmdMatrix34_t GetMatrix34TrackedDeviceProperty(uint unDeviceIndex,TrackedDeviceProperty prop,ref TrackedPropertyError pError);

 public abstract uint GetStringTrackedDeviceProperty(uint unDeviceIndex,TrackedDeviceProperty prop,System.Text.StringBuilder pchValue,uint unBufferSize,ref TrackedPropertyError pError);

 public abstract float GetFloatTrackedDeviceProperty(uint unDeviceIndex,TrackedDeviceProperty prop,ref TrackedPropertyError pError);

 public abstract int GetInt32TrackedDeviceProperty(uint unDeviceIndex,TrackedDeviceProperty prop,ref TrackedPropertyError pError);

 public abstract bool GetBoolTrackedDeviceProperty(uint unDeviceIndex,TrackedDeviceProperty prop,ref TrackedPropertyError pError);

 string GetStringProperty(TrackedDeviceProperty prop)
 {
     var error = TrackedPropertyError.TrackedProp_Success;
     var capactiy = hmd.GetStringTrackedDeviceProperty(OpenVR.k_unTrackedDeviceIndex_Hmd, prop, null, 0, ref error);
     if (capactiy > 1)
     {
         var result = new System.Text.StringBuilder((int)capactiy);
         hmd.GetStringTrackedDeviceProperty(OpenVR.k_unTrackedDeviceIndex_Hmd, prop, result, capactiy, ref error);
         return result.ToString();
     }
     return (error != TrackedPropertyError.TrackedProp_Success) ? error.ToString() : "<unknown>";
 }

 float GetFloatProperty(TrackedDeviceProperty prop)
 {
     var error = TrackedPropertyError.TrackedProp_Success;
     return hmd.GetFloatTrackedDeviceProperty(OpenVR.k_unTrackedDeviceIndex_Hmd, prop, ref error);
 }

internal static extern int SteamAPI_vr_IVRSystem_GetInt32TrackedDeviceProperty(IntPtr instancePtr, TrackedDeviceIndex_t unDeviceIndex, TrackedDeviceProperty prop, ref TrackedPropertyError pError);