C# How to import ntdll.dll to use NtDelayExecution and ZwSetTimerResolution?

Question

I am new to C# and I am trying to use the NtDelayExecution and ZwSetTimerResolution functions from ntdll.dll in order to create a custom sleep timer. (Thread.sleep is not precise enough for my application). I have tried many different ways, but i'm not sure how to import ntdll.dll in order to use these two functions. The two static NTSTATUS lines are partial c++ that I am trying to convert to C#. What I have tried so far:

public unsafe static void GoSleep(float ms, float resolution = 0.5f)
        {

            if (resolution < 0.5) resolution = 0.5f;
            if (ms < resolution) ms = resolution;
         
            nuint res = (nuint)(resolution * 10000);
            nuint actualRes = 0;

            [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            internal static extern IntPtr GetProcAddress(IntPtr hModule, string procName);

            [DllImport("kernel32.dll", CharSet=CharSet.Unicode, SetLastError=true)]
            public static extern IntPtr GetModuleHandle([MarshalAs(UnmanagedType.LPWStr)] in string lpModuleName);

            static NTSTATUS(__stdcall* NtDelayExecution)(bool Alertable, PLARGE_INTEGER DelayInterval) = (NTSTATUS(__stdcall*)(bool, PLARGE_INTEGER)) GetProcAddress(GetModuleHandle(X("ntdll.dll")), X("NtDelayExecution"));
            static NTSTATUS(__stdcall* ZwSetTimerResolution)(IN nuint RequestedResolution, IN bool Set, OUT pnuint ActualResolution) = (NTSTATUS(__stdcall*)(ULONG, BOOLEAN, PULONG)) GetProcAddress(GetModuleHandle(X("ntdll.dll")), X("ZwSetTimerResolution"));

            ZwSetTimerResolution(res, true, &actualRes);
         
            long LargeInteger = -1 * (long)(ms * 10000.0f);
         
            
            NtDelayExecution(false, &LargeInteger);
         
            ZwSetTimerResolution(res, false, &actualRes);
        }

Answer 1

The easiest way to import it is to use nuget.

1. Right click on nuget manager

2. Enter ntdll.dll, then select install