报错：具有键"..."的ViewData项属于类型"..."，但它必须属于类型"IEnumerable<SelectListItem>"

报错：具有键"..."的ViewData项属于类型"..."，但它必须属于类型"IEnumerable<SelectListItem>"

 

□ 背景分析

MVC控制器中有2个方法，一个是用来显示添加视图，另一个是用来接收添加数据。

public ActionResult Add()

{

    ViewData["o"] = 类型为List<SelectListItem>的集合实例;

    return View();

}

[HttpPost]

public ActionResult Add(SomeViewModel model)

{

    if(ModelState.IsValid)

    {

        //TO DO

    }

    else

    {

        return View(model);

    }

}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

 

□ 解决方法

控制器方法Add()在接收视图传来的view model,在验证失败的情况下，返回到显示添加的视图，这时，同样需要把类型为List<SelectListItem>的集合实例传递到前台视图。正确的写法是：

[HttpPost]

public ActionResult Add(SomeViewModel model)

{

    if(ModelState.IsValid)

    {

        //TO DO

    }

    else

    {

        ViewData["o"] = 类型为List<SelectListItem>的集合实例;

        return View(model);

    }

}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }