Question

我正在尝试使用JsonConvert.DeserializeObject使用json数据绑定asp：dropdownlist，它正在获取完整的json，但我想将其与json数据的内部数组绑定。提取的数据类型为{System.Collections.ListDictionaryInternal}，绑定时抛出异常{"Data source is an invalid type. It must be either an IListSource, IEnumerable, or IDataSource."}。

ddlCategoryMain完全绑定，

ddlCategorySub

上绑定ddlCategoryMain_SelectedIndexChanged的例外情况

这是json数据：

 {
  "Category": [
    {
      "MainCategory": "Biography",
      "SubCategory": [
        "Historical",
        "Political",
        "Military",
        "Musician"
      ]
    },
    {
      "MainCategory": "Business",
      "SubCategory": [
        "Self-Employed",
        "Taxation",
        "Personal Finance",
        "Organisational Behaviour"
      ]
    },
    {
      "MainCategory": "Computers & Internet",
      "SubCategory": [
        "Computer Programing",
        "Web Design",
        "Mobile Phones",
        "Computer Hardware",
        "Operating Systems"
      ]
    }
  ]
}

这是DataEntity：

public class bookcategoryDE
{
    public List<Category> Category { get; set; }
}
public class Category
{
    public int CategoryID { get; set; }
    public string MainCategory { get; set; }
    public List<string> SubCategory { get; set; }
}

这是我的代码：

（ASPX）：

<asp:DropDownList ID="ddlCategoryMain" runat="server" DataTextField="MainCategory" DataValueField="MainCategory"
            AutoPostBack="true" OnSelectedIndexChanged="ddlCategoryMain_SelectedIndexChanged">
        </asp:DropDownList>
        <br />
        <br />
        <asp:DropDownList ID="ddlCategorySub" runat="server" DataTextField="SubCategory" DataValueField="SubCategory"></asp:DropDownList>

（CS）：

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {



            var JsonBookCategory = ReadJson<bookcategoryDE>(Server.MapPath("~/Json/Category.json"));
            ddlCategoryMain.DataSource = JsonBookCategory.Category;
            ddlCategoryMain.DataBind();
        }
    }

    public T ReadJson<T>(string JsonPath)
    {
        using (StreamReader r = new StreamReader(JsonPath))
        {
            T keys = JsonConvert.DeserializeObject<T>(r.ReadToEnd());
            return keys;
        }
    }

    protected void ddlCategoryMain_SelectedIndexChanged(object sender, EventArgs e)
    {
        var JsonBookCategory = ReadJson<bookcategoryDE>(Server.MapPath("~/Json/Category.json"));
        ddlCategorySub.DataSource = JsonBookCategory;
        ddlCategorySub.DataBind();
    }

Answer 1

protected void ddlCategoryMain_SelectedIndexChanged(object sender, EventArgs e)
{
    var JsonBookCategory = ReadJson<bookcategoryDE>(Server.MapPath("~/Json/Category.json"));
    // JsonBookCategory is not IListSource, IEnumerable, or IDataSource(like say exception)
    //ddlCategorySub.DataSource = JsonBookCategory;
    var selectedCategoryName  = ddlCategoryMain.SelectedValue;
    var selectedCategory = JsonBookCategory.Category.Where(c => c.MainCategory== selectedCategoryName).SingleOrDefult();
    if(selectedCateogry != null)
    {
     ddlCategorySub.DataSource = selectedCategory.Category;
     ddlCategorySub.DataBind();
    }

}

也许你的下拉配置应该是......

       <asp:DropDownList ID="ddlCategoryMain" runat="server" DataTextField="MainCategory" DataValueField="MainCategory"
        AutoPostBack="true" OnSelectedIndexChanged="ddlCategoryMain_SelectedIndexChanged">
    </asp:DropDownList>
    <br />
    <br />
    <asp:DropDownList ID="ddlCategorySub" runat="server" DataTextField="MainCategory" DataValueField="MainCategory"></asp:DropDownList>

“{”数据源是无效类型。它必须是IListSource，IEnumerable或IDataSource。“}”绑定时

1 个答案: