/// <summary>
/// 计算文件夹B相对文件夹A的相对路路径
/// </summary>
/// <param name="pathA">确定是绝对路径</param>
/// <param name="pathB">也要是绝对路径</param>
string CalculateRelativePath(string pathA, string pathB)
{
    if (string.IsNullOrEmpty(pathA) || string.IsNullOrEmpty(pathB))
        throw new Exception("路径不能为空额");
    if (pathA.Equals(pathB)) return "";

    char[] temp = new char[] { '/', '\\' };
    string[] tempA = pathA.Split(temp);
    string[] tempB = pathB.Split(temp);

    // 最长路径层级
    int maxLength = (tempB.Length > tempA.Length) ? tempB.Length : tempA.Length;
    // 相同层级数量
    int sameFolderCount = 0;
    for (int i = 0; i < maxLength; i++)
    {
        if (tempA[i] == tempB[i])
            ++sameFolderCount;
        else
            break;
    }
    // 最大不同层级数量
    int diffFolderCount = maxLength - sameFolderCount;

    System.Text.StringBuilder builder = new System.Text.StringBuilder();
    while (diffFolderCount-- > 0)
        builder.Append("../");

    for (int i = sameFolderCount; i < tempB.Length; i++)
    {
        builder.Append(tempB[i]);
        builder.Append("/");
    }

    return builder.ToString().TrimEnd('/');
}