由于您要删除一些行，但回发在整个集合保存提交操作，你的索引可能是没有启动一个零，或者是不连续的。在删除第1行的情况下，帐值

NorthOrderDetails[1].Quantity=SomeValue&NorthOrderDetails[1].UnitPrice=SomeOtherValue

有没有值 NorthOrderDetails [0] ... 这样的绑定失败，集合为空。

默认情况下， DefaultModelBinder 需要收集索引来从零开始，并是不连续的。当你删除一个项目，从DOM删除其控制，集合无法正确绑定。为了使这项工作，你需要添加一个额外的隐藏输入该 DefaultModelBinder 用来匹配集合属性。更改视图code到

 ％的for（int i = 0; I＆LT; Model.NorthOrderDetails.Count;我++）
{％GT;
  ＆所述; TR＆GT;
    ＆LT; TD＆GT;＆LT;％：Html.DisplayFor（M = GT; m.NorthOrderDetails [I] .ProductID）％GT;＆LT; / TD＆GT; //删除的ToString（）
    ＆LT; TD＆GT;＆LT;％：Html.DisplayFor（M = GT; m.NorthOrderDetails [I] .ProductName）％GT;＆LT; / TD＆GT;
    ＆所述; TD＆GT;
      ＆LT;输入类型=隐藏的名字=NorthOrderDetails.IndexVALUE =＆LT;％：我％GT; /＆GT; //添加此
      ＆LT;％：Html.TextBoxFor（M = GT; m.NorthOrderDetails [I] .Quantity）％GT;
    ＆LT; / TD＆GT;
    ＆LT; TD＆GT;＆LT;％：Html.TextBoxFor（M = GT; m.NorthOrderDetails [I] .UnitPrice）％GT;＆LT; / TD＆GT;
    ＆LT; TD＆GT;＆LT;按钮式=按钮级=删除数据-ID =＆LT;％：Model.NorthOrderDetails [I] .ProductID％GT;＆GT;删除＆LT; /按钮＆GT;＆LT; TD＆GT;
    ＆LT; TD＆GT;＆LT;输入类型=隐藏的名字=＆LT;％：Model.NorthOrderDetails [I] .ProductName％GT;值=＆LT;％：我％GT; /＆GT;＆下; TD＆GT;
  ＆所述; TR＆GT;
＆LT;％}％GT;
 

注：我早已忘记ASPX，但剃刀code为隐藏输入＆LT;输入类型=隐藏的名字=NorthOrderDetails.IndexVALUE =@我 /方式＆gt; ，所以你可能要检查我的语法

旁注：

1. 您使用session似乎不妥这里。在删除
   方法，要删除的项目。当你终于救
   收集，你需要从一开始的原始集合
   数据库并加以比较，以确定在要删除的项
   数据库。相反，你删除（）方法应该调用
   数据库删除的项目（见我的回答你的$p$pvious
   问题）


2. 您添加按钮不应该是，一个提交并发布到
   视图2（）方法。

I have a table:

<% using(Html.BeginForm("View2","Order"))
{  %>  
<table id="Products" class="Products">
    <tr>
        <th>ProductId</th>
        <th>Productname</th>
        <th>Quantity</th>
        <th>UnitPrice</th>
    </tr>
    <% for(int i=0; i < Model.NorthOrderDetails.Count; i++)
       {                            %>
              <tr>
        <td><%: Html.Label(Model.NorthOrderDetails[i].ProductID.ToString()) %></td>
        <td><%: Html.Label(Model.NorthOrderDetails[i].ProductName) %> </td>
        <td><%: Html.TextBoxFor(m => m.NorthOrderDetails[i].Quantity) %></td>
        <td><%: Html.TextBoxFor(m => m.NorthOrderDetails[i].UnitPrice) %></td>
          <td><button type="button" class="delete" data-id="<%:Model.NorthOrderDetails[i].ProductID %>">Delete</button><td> 
    <td><input type="hidden" name="<%:Model.NorthOrderDetails[i].ProductName %>" value="<%:i %>" /><td>
 <tr>
    <% } %>

</table>
<input type="submit" name="button" value="Add" /> 
<input type="submit" name="button" value="Save" /> 
<% } %>  

When I click the delete button I'm calling this script:

<script type="text/javascript">
          var url = '<%:Url.Action("Delete", "Order")%>';
          $('.delete').click(function () {
              var id = $(this).data('id'); // Get the product ID
              var row = $(this).closest('tr');// Get the table row
              $.post(url, { ID: id }, function () {
                  row.remove(); // remove the row from the table
                                });
          });

            </script>

And the script call this method in the Controller

[HttpPost]
public JsonResult Delete(int ID)
{
    NorthOrder forOrderDetail = (NorthOrder)Session["Order"];
    forOrderDetail.NorthOrderDetails.RemoveAll(z => z.ProductID == ID);
    Session["Order"] = forOrderDetail;

    return Json(null);
}

In the UI the row deletes correctly when I click on the submit button. But In the controller method the count of the collection equal null when I delete the first row, and it's equals to 1 when I delete the last row For example, table contains two rows when page loaded

public ActionResult View2(NorthOrder q,  string button)
{
}

Why?

Because you are deleting some rows, but posting back the whole collection in the Save submit action, your indexers are either not starting a zero, or are non consecutive. In the case of deleting the 1st row, the posted values are

NorthOrderDetails[1].Quantity=SomeValue&NorthOrderDetails[1].UnitPrice=SomeOtherValue

There are no values with NorthOrderDetails[0]... so binding fails and the collection is empty.

By default, the DefaultModelBinder require collection indexers to start at zero and be non-consecutive. When you delete an item and remove its controls from the DOM, the collection cannot be bound correctly. To make this work you need to add an extra hidden input which the DefaultModelBinder uses to match up collection properties. Change the view code to

% for(int i=0; i < Model.NorthOrderDetails.Count; i++)
{%>
  <tr>
    <td><%: Html.DisplayFor(m => m.NorthOrderDetails[i].ProductID) %></td> // Remove the .ToString()
    <td><%: Html.DisplayFor(m => m.NorthOrderDetails[i].ProductName) %></td>
    <td>
      <input type="hidden" name="NorthOrderDetails.Index" value="<%: i %>" /> // add this 
      <%: Html.TextBoxFor(m => m.NorthOrderDetails[i].Quantity) %>
    </td>
    <td><%: Html.TextBoxFor(m => m.NorthOrderDetails[i].UnitPrice) %></td>
    <td><button type="button" class="delete" data-id="<%:Model.NorthOrderDetails[i].ProductID %>">Delete</button><td> 
    <td><input type="hidden" name="<%:Model.NorthOrderDetails[i].ProductName %>" value="<%:i %>" /><td>
  <tr>
<% } %>

Note: I have long forgotten aspx, but the razor code for the hidden input is <input type="hidden" name="NorthOrderDetails.Index" value="@i" /> so you may want to check my syntax.

Side notes:

1. Your use of session seems inappropriate here. In the Delete method, you are removing the item. When your finally save the collection, you would need to get the original collection from the database and compare them to determine which items to delete in the database. Instead, you Delete() method should be calling the database to delete the item (refer my answer to your previous question)
2. Your Add button should not be, a submit and posting to the View2() method.