Godot 4 C# RenderingServer material

using Godot;

public partial class RenderServerTest : Node3D
{
    private Rid meshInstanceRid;
    private Rid meshRid;
    private Rid materialRid;
    private Rid shaderRid;

    public override void _Ready()
    {
        var mesh = new BoxMesh();
        if (mesh == null){
            GD.PrintErr("Failed to load mesh from: " + ObjFilePath);
            return;
        }

        materialRid = RenderingServer.MaterialCreate();

        Shader shader = GD.Load<Shader>("res://red.gdshader");
        var shaderRid = RenderingServer.ShaderCreate();
        RenderingServer.ShaderSetCode(shaderRid, shader.Code);
        RenderingServer.MaterialSetShader(materialRid, shaderRid);

        meshRid = RenderingServer.MeshCreate();
        for (int i = 0; i < mesh.GetSurfaceCount(); i++) {
            RenderingServer.MeshAddSurfaceFromArrays(
                meshRid,
                RenderingServer.PrimitiveType.Triangles,
                mesh.SurfaceGetArrays(i)
            );
            RenderingServer.MeshSurfaceSetMaterial(meshRid, i, materialRid);

        }
        meshInstanceRid = RenderingServer.InstanceCreate();
        RenderingServer.InstanceSetBase(meshInstanceRid, meshRid);

        Transform3D transform = Transform3D.Identity;
        transform.Origin = new Vector3(0, 10f, 0);
        RenderingServer.InstanceSetTransform(meshInstanceRid, transform);

        RenderingServer.InstanceSetScenario(meshInstanceRid, GetWorld3D().Scenario);

    }

    public override void _ExitTree()
    {
        RenderingServer.FreeRid(meshInstanceRid);
        RenderingServer.FreeRid(meshRid);
        RenderingServer.FreeRid(materialRid);
    }
}