Tips for passing a "NULL" value into a nullable field when making a call from JavaScript to an ASP.NET WebService

Is there a way to pass the value of "NULL" into a nullable field when calling an ASP.NET WebService from JavaScript?

I am currently calling the method in this manner from JavaScript:

ws_data.SaveTasks(eval({"MyValue":"null"}), OnSaveComplete, OnError, OnTimeOut);

However, I encounter an error (which triggers the OnError function):

null is not a valid value for Int32

Interestingly, if I pass a valid integer instead of "null", everything works perfectly fine.

I need guidance: What am I doing wrong? How can I correctly pass a 'null' value that will be interpreted as a NULL .NET object?

Any suggestions or ideas would be greatly appreciated!

P.S. Additional details are provided below.

Here is the key part of MyData declaration:

public class MyData
{
    ...
    public int? MyValue { get; set; }
}

Declaration of the ASP.NET web service goes like this:

[WebService(Namespace = "...")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]
public class ws_data : WebService
{
    [WebMethod(true)]
    public object SaveData(MyData data)
    {...}
}

And the ws_data is referenced through ScriptManager:

<asp:ScriptManager runat="server">
        <Services>
            <asp:ServiceReference Path="/ws_data.asmx" />
        </Services>
    </asp:ScriptManager>

Answer №1

The reason for the issue is that the string null is being passed instead of the actual null value. To resolve this, simply remove the quotes around null to represent it as an actual null.

{"MyValue": null}

Regarding the eval function, it seems unnecessary in this context. The eval function is designed to evaluate a string as JavaScript code, but in this case, it can be omitted.

ws_data.SaveTasks({"MyValue": null}, OnSaveComplete, OnError, OnTimeOut);

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