UnityEngine.NavMeshAgent.CalculatePath C# (CSharp) Method

        public bool CalculatePath(Vector3 targetPosition, NavMeshPath path)
        {
            path.ClearCorners();
            return this.CalculatePathInternal(targetPosition, path);
        }

    // Unity's example function..
    public float CalculatePathLength(NavMeshAgent nav, Vector3 targetPosition)
    {
        // Added condition since it was returning impossible values if given same position :P
        if (nav.transform.position == targetPosition)
            return 0;

        // Create a path and set it based on a target position.
        var path = new NavMeshPath();
        if (nav.enabled)
            nav.CalculatePath(targetPosition, path);

        // Create an array of points which is the length of the number of corners in the path + 2.
        var allWayPoints = new Vector3[path.corners.Length + 2];

        // The first point is the player position.
        allWayPoints[0] = player.transform.position;

        // The last point is the enemy position
        allWayPoints[allWayPoints.Length - 1] = targetPosition;

        // The points inbetween are the corners of the path.
        for (var i = 0; i < path.corners.Length; i++)
            allWayPoints[i + 1] = path.corners[i];

        // Create a float to store the path length that is by default 0.
        float pathLength = 0;

        // Increment the path length by an amount equal to the distance between each waypoint and the next.
        for (int i = 0; i < allWayPoints.Length - 1; i++)
        {
            pathLength += Vector3.Distance(allWayPoints[i], allWayPoints[i + 1]);
        }

        return pathLength;
    }