c# - string.IsNullOrEmpty(string)' 有一些无效参数

Question

我将 MVC 3.5 转换为 MVC2 4.0，出现错误 The best overloaded method match for 'string.IsNullOrEmpty(string)' has some invalid arguments这是我的代码:

<% if (this.Model.VisitId == 0) { %>
        mustSave = true;
    <% } else { %>
        mustSave = false;
    <% } %>
    <% if (String.IsNullOrEmpty(Html.ValidationSummary())) { %>
        dataChanged = false;
    <% } else { %>
        dataChanged = true;
    <% } %>

提前致谢

Answer 1

Html.ValidationSummary() 返回 MvcHtmlString，而不是普通字符串。所以，试试这个:

<% if (MvcHtmlString.IsNullOrEmpty(Html.ValidationSummary())) { %>