how do i use a c# array as a nativearray without copying the data? in csharp

You can use the System.Runtime.InteropServices.GCHandle struct to pin the managed array in memory and obtain a pointer to it. This allows you to pass the pointer to unmanaged code and treat it as a native array without copying the data.

main.cs
using System;
using System.Runtime.InteropServices;

class Program
{
    static void Main(string[] args)
    {
        int[] managedArray = { 1, 2, 3, 4, 5 };

        GCHandle handle = GCHandle.Alloc(managedArray, GCHandleType.Pinned);

        IntPtr nativePtr = handle.AddrOfPinnedObject();

        // Pass `nativePtr` to unmanaged code as a pointer to a native array.

        handle.Free();
    }
}
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The GCHandleType.Pinned value indicates that the handle is pinned in memory, and the AddrOfPinnedObject() method returns a pointer to the pinned object. Once you're done with the native array, you need to call handle.Free() to release the pinned handle.

Note that it's important to keep the managed array pinned for as short a time as possible to minimize the impact on garbage collection.