我在Razor View 引擎中使用了MVC3(VB),并且在使用图表助手来创建许多图表。我有此代码的工作:

在 View 中:

<img src="@Url.Action("Rpt002", "Chart", New With {.type = "AgeGender"})" alt="" />

这会在Chart Controller 中触发此操作:
    Function Rpt002(type As String) As ActionResult
        Dim chart As New System.Web.Helpers.Chart(300, 300)
        '...code to fill the chart...
        Return File(chart.GetBytes("png"), "image/png")
    End Function

因为我在许多 View 上都有许多图表,所以我想将img的创建放入帮助函数中。我认为以下方法会起作用:
<System.Runtime.CompilerServices.Extension>
Public Function ReportChart(htmlHelper As HtmlHelper, action As String, type As String) As MvcHtmlString

    Dim url = htmlHelper.Action(action, "Chart", New With {.type = type})
    Return New MvcHtmlString(
        <img src=<%= url %> alt=""/>
    )

End Function

当我尝试这样做时,出现以下错误:
OutputStream is not available when a custom TextWriter is used.

我以为调用“htmlHelper.Action”会生成URL,因此我可以将其添加到img中,但实际上是在触发操作。如何从扩展方法中获得等效的“Url.Action”?

最佳答案

只需实例化UrlHelper并在其上调用Action方法:

Dim urlHelper as New UrlHelper(htmlHelper.ViewContext.RequestContext);
Dim url = urlHelper.Action(action, "Chart", New With {.type = type})

另外,我建议您使用TagBuilder来确保所生成的标记有效并且属性正确编码:
<System.Runtime.CompilerServices.Extension> _
Public Shared Function ReportChart(htmlHelper As HtmlHelper, action As String, type As String) As IHtmlString
    Dim urlHelper = New UrlHelper(htmlHelper.ViewContext.RequestContext)
    Dim url = urlHelper.Action(action, "Chart", New With { _
        Key .type = type _
    })
    Dim img = New TagBuilder("img")
    img.Attributes("src") = url
    img.Attributes("alt") = String.Empty
    Return New HtmlString(img.ToString())
End Function

关于asp.net-mvc-3 - 如何在扩展方法中获取Url.Action,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/7531846/

10-12 12:43
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