通行证清单 <int> 从后面的代码在Javascript函数中使用

Question

Currently I have a Javascript function that uses I can hard code values in like -

data: [1,4,7,9]

However I wish to pass in an integer list to set the values from the code behind something like -

C# Code Behind

public List<int> listOfInts = new List<int>();

protected void Button1_Click(object sender, EventArgs e)
    {
        listOfInts.Add(1);
        listOfInts.Add(4);
        listOfInts.Add(7);
        listOfInts.Add(9);

        ScriptManager.RegisterStartupScript(this, GetType(), "blah", "JSfunction()", true);
    }

Aspx

data: <% = listOfInts %>

However this breaks with the error -

0x800a1391 - Microsoft JScript runtime error: 'JSfunction' is undefined

If I remove the aforementioned line and do it like this in the function (not passing anything from the code behind like I need to) -

var listOfInts = new Array(); 
listOfInts[0] = 1;
listOfInts[1] = 2; 
listOfInts[2] = 3; 
listOfInts[3] = 4;

and then set -

data: [listOfInts[0],listOfInts[1],listOfInts[2],listOfInts[3]]

This works fine. How can I pass the values from the code behind to populate the values in the Javascript function?

Answer 1

You need to format listOfInts as a javascript array. Try adding a property in your code-behind like this:

protected string IntsAsJSArray
{   
    get 
    {
        return string.Format("[{0}]", string.Join(",", listOfInts));
    }
}

Then in your ASPX page

data: <%= IntsAsJSArray %>

Answer 2

A more generic method to do this... and significantly better in my opinion would be to write something that works for any object you needed to do this for. Consider the following extension methods...

    public static T FromJson<T>(this string jsonData, Encoding encoding = null) 
        where T : class
    {
        encoding = encoding ?? Encoding.Default;
        var deserializer = new DataContractJsonSerializer(typeof(T));
        var buffer = encoding.GetBytes(jsonData);
        using (var stream = new MemoryStream(buffer))
        {
            return deserializer.ReadObject(stream) as T;
        }
    }

    public static string ToJson<T>(this T obj, Encoding encoding = null) 
        where T : class
    {
        encoding = encoding ?? Encoding.Default;
        var serializer = new DataContractJsonSerializer(typeof(T));
        using (var stream = new MemoryStream())
        {
            serializer.WriteObject(stream, obj);
            return encoding.GetString(stream.ToArray());
        }
    }

Usage then looks like this in your case...

data: <% = listOfInts.ToJson() %> 

This works whether you have a List, Int[], or any other object for that matter on your asp.net side. Also don't forget to consider what encoding your JSON text is in.