Question

有没有办法追加ul class =＆＃34; nav nav-third-level background-white collapse＆＃34;只有第一次循环到达那里？我试过，bool和一个计数器，但显然它每次都被初始化，我试着跳过增量，但这样它甚至不能初始化它：）

我试图获取以下HTML代码：

<li class="">
    <a href="#"><i class="fa fa-fw"></i>First Level<span class="fa arrow"></span></a>
    <ul class="nav nav-second-level background-white collapse">
        <li>
            <a href="#">Second Level1</a>
            <ul class="nav nav-third-level background-white collapse">
                <li>
                    <a href="#">Third Level1</a>
                </li>
                <li>
                    <a href="#">Third Level2</a>
                </li>
            </ul>
            </li>
        <li>
            <a href="#">Second Level2</a>
            <ul class="nav nav-third-level background-white collapse">
                <li>
                    <a href="#">Third Level4</a>
                </li>
                <li>
                    <a href="#">Third Level5</a>
                </li>
            </ul>
        </li>           
    </ul>
</li>

这是我的C＃代码：

private static string RenderMenuRecursive(ItemMenu menu, int level)
{
    StringBuilder sb = new StringBuilder();
    if (level > 0)
    {
        int firstIteration = 0; // This will be initialized as 0 every time :\

        if (level == 1)
        {
            sb.AppendLine("<li class=\"\"><a href=\"#\"><i class=\"fa fa-fw\"></i>"+ menu.name + "<span class=\"fa arrow\"></span></a>");
        }
        if (level == 2)
        {
            sb.AppendLine("<ul class=\"nav nav-second-level background-white collapse\"><li><a href=\"#\">" + menu.name + "</a>");
        }
        if (level == 3)
        {
            if (firstIteration == 0)
            {
                sb.AppendLine("<ul class=\"" + "nav nav-third-level background-white collapse" + "\">");
                firstIteration++;
            }

            sb.AppendLine("<li><a href=\"#\">" + menu.name + "</a></li>");
        }

    }

    level++;

    foreach (ItemMenu subMenu in menu.subMenuItems)
    {
        sb.AppendLine(RenderMenuRecursive(subMenu, level));
    }

    return sb.ToString();
}

这就是我实际得到的：

<li class=""><a href="#"><i class="fa fa-fw"></i>First Level<span class="fa arrow"></span></a>
<ul class="nav nav-second-level background-white collapse"><li><a href="#">Second Level1</a>
<ul class="nav nav-third-level background-white collapse">
<li><a href="#">Third Level1</a></li>

<ul class="nav nav-third-level background-white collapse">
<li><a href="#">Third Level2</a></li>

<ul class="nav nav-second-level background-white collapse"><li><a href="#">Second Level2</a>
<ul class="nav nav-third-level background-white collapse">
<li><a href="#">Third Level3</a></li>

<ul class="nav nav-third-level background-white collapse">
<li><a href="#">Third Level4</a></li>

Answer 1

您在错误的位置定义和初始化变量。由于您为每次迭代调用方法，因此您的变量将获得一个新的范围，并在每次迭代中进行初始化。

如果你想在for-each循环中调用方法，你需要让方法知道你在哪个迭代中。例如通过引入一个参数：

private static string RenderMenuRecursive(ItemMenu menu, int level, bool firstIteration)
{
    [...]

        if (level == 3)
        {
            if (firstIteration)
            {
                sb.AppendLine("<ul class=\"" + "nav nav-third-level background-white collapse" + "\">");
                firstIteration++;
            }

            sb.AppendLine("<li><a href=\"#\">" + menu.name + "</a>");
        }

    [...]

    var firstIteration = true;

    foreach (ItemMenu subMenu in menu.subMenuItems)
    {
        sb.AppendLine(RenderMenuRecursive(subMenu, level, firstIteration));
        firstIteration = false;
    }

    return sb.ToString();
}

需要说明的是，此问题与渲染，StringBuilders，HTML或MVC无关。这只是如何使用嵌套（递归）方法调用和状态...

的问题

Answer 2

问题在于 int firstIteration = 0; 它总是设置为0，因为它不是静态成员（你应该避免使用静态成员）

你应该在你的方法RenderMenuRecursive（subMenu，level， renderUl ）中添加param并移动

int firstIteration = 0; //每次

初始化为0

到

int firstIteration = 0;

foreach (ItemMenu subMenu in menu.subMenuItems)
{
    sb.AppendLine(RenderMenuRecursive(subMenu, level, firstInteration == 0));

    firstIteration++; 
}

还要考虑方法名称更改，因为没有递归调用。

仅在循环的第一次迭代时渲染字符串

2 个答案: