UnityEditor.InternalMeshUtil.CalcTriangleCount C# (CSharp) Method

        public static extern int CalcTriangleCount(Mesh mesh);
        [MethodImpl(MethodImplOptions.InternalCall)]

        public static void SetPerTriangleUV2(Mesh src, Vector2[] triUV)
        {
            int triCount = InternalMeshUtil.CalcTriangleCount(src);
            int uvCount  = triUV.Length;

            if (uvCount != 3 * triCount)
            {
                Debug.LogError("mesh contains " + triCount + " triangles but " + uvCount + " uvs are provided");
                return;
            }

            SetPerTriangleUV2NoCheck(src, triUV);
        }