使用DropDown和ViewData进行筛选

Question

我一直在四处搜索论坛，所以试图让我的索引页面使用下拉菜单进行筛选。

这是我想出来的。

我所有的控制器首先是这样的：

public ActionResult Index(string searchString) 
    { 
     var projects = from s in db.Project select s; 
     var themeList = db.Theme.ToList(); 
     var projectList = db.Project.ToList(); 

     if (Request.Form["FilterTheme"] != null && Request.Form["FilterTheme"] != "") 
     { 
      int i = int.Parse(Request.Form["FilterTheme"]); 
      projects = from s in db.Project 
         from c in s.Themes 
         where c.ThemeID == i 
         select s;    
     } 

     if (Request.Form["Styles"] != null && Request.Form["Styles"] != "") 
     { 
      int i = int.Parse(Request.Form["Styles"]); 
      projets = from s in db.Project 
         where s.ID == i 
         select s; 
     } 

     ViewData["Theme"] = new SelectList(themeList,"ThemeID", "Name"); 
     ViewData["Style"] = new SelectList(projectList, "ID", "Style"); 

     return View(projects); 
    } 

和视图的样子：

@using (Html.BeginForm()) 
{ 
<table> 
    <thead> 
     <tr align="left"> 
      <th> 
       Project name : 
      </th> 
      <th> 
       Theme(s) : 
       <br /><br /> 
       @Html.DropDownList("FilterTheme", (SelectList)ViewData["Theme"], "Select a theme", new { onchange = "this.form.submit()" }) 
      </th> 
      <th> 
       Style : 
       <br /><br /> 
       @Html.DropDownList("Styles", (SelectList)ViewData["Style"], "Select a style", new { onchange = "this.form.submit()" }) 
      </th> 
      <th> 
       Date : 
      </th> 
     </tr>  
    </thead> 

    <tbody> 
     ... 
    </tbody> 
</table> 
} 

终于成功了！

现在，如果我想删除我的样式下拉内的重复项，将如何工作？

Answer 1

那么让我们先从明显的事情，你需要命名的对象比较好，如果你有，你会看到这个明显的很快的问题，看看：

/*if (Request.Form["Style"] != null && Request.Form["Style"] != "") 
    { 
     int i = int.Parse(Request.Form["Style"]); 
     projets = from s in db.Project 
        from c in s.Style 
        where s.ID == i 
        select s; 
    }*/ 

要设置I =的风格，但你正在检查其对项目的ID，这里改名是你目前有：

if (Request.Form["Style"] != null && Request.Form["Style"] != "") 
    { 
     int styleID = int.Parse(Request.Form["Style"]); 
     projects = from projects in db.Project 
        from styles in projects.Style 
        where projects.ID == styleID 
        select projects; 
    } 

我猜这是你真正想要的：

if (Request.Form["Style"] != null && Request.Form["Style"] != "") 
    { 
     int styleID = int.Parse(Request.Form["Style"]); 
     projects = (from projects in db.Project 
        where projects.StyleID == styleID 
        select projects).Distinct(); 
    } 

按照要求，我添加了一个.Distinct（）在那里删除重复。这里有一些资源：

http://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b http://blogs.msdn.com/b/charlie/archive/2006/11/19/linq-farm-group-and-distinct.aspx

Answer 2

不应该为DropDownList第一个参数和ViewData使用相同的名称。在你的情况下，你使用了两次Style这是错误的。您应该使用一个独立的名字：

@Html.DropDownList(
    "SelectedStyle", 
    (SelectList)ViewData["Styles"], 
    "Select a style", 
    new { onchange = "this.form.submit()" } 
) 

和控制器：

public ActionResult Index(int? filterTheme, int? selectedStyle) 
{ 
    var projects = from s in db.Project select s; 

    if (filterTheme != null) 
    { 
     projects = from s in db.Project 
        from c in s.Themes 
        where c.ThemeID == filterTheme.Value 
        select s;    
    } 

    if (selectedStyle != null) 
    { 
     projects = from s in projects 
        from c in s.Style 
        where s.ID == selectedStyle.Value 
        select s; 
    } 

    ViewData["Theme"] = new SelectList(db.Theme.ToList(), "ThemeID", "Name"); 
    ViewData["Styles"] = new SelectList(db.Project.ToList(), "ID", "Style"); 

    return View(projects); 
}