Pass a nullable parameter using jquery .ajax

Question

I have a following situation

function Insert(name, parentID) {

            $.ajax({
                type: "POST",
                url: "topic.aspx/Insert",
                data: JSON.stringify({
                    "name": name,
                    "parentID": undefined
                }),
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (msg) {


                },
                error: function (msg) { alert(msg.responseText); }


            });
            }

And C# looks like this

[WebMethod]
        public static int Insert(string name, int? parentID)
        {
            GM.KnowledgeBase.Business.Topics topics = new GM.KnowledgeBase.Business.Topics();
            return topics.Insert(name, parentID);
        }

When parentID is null or undefined I get "Invalid web service call, missing value for parameter". Is there a more elegant way to solve this issue other then passing a parameter as a string and detecting if string is empty?

Good idea, but the param is not passed if it is null. JSON.stringify does not include it in json output. So the solution is in modifying input params in C# for method Insert(). — mko
– mko, Commented Jun 9, 2014 at 12:43

Johan · Accepted Answer · 2014-06-09 12:34:42Z

2

Don't pass it when it's not defined?

function Insert(name, parentID) {

    var data = { name: name };

    if(parentID)
        data.parentID = parentID

        $.ajax({
            type: "POST",
            url: "topic.aspx/Insert",
            data: data,
            // etc...
       });
}

or if your webmethod can parse null, this should do:

data: JSON.stringify({
    "name": name,
    "parentID": parentID || null
}),

answered Jun 9, 2014 at 12:34

Johan

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6 Comments

mko Over a year ago

it will be expected. maybe creating override method without parendID? is that what you are saying?

Johan Over a year ago

@John Since it's nullable, try my latter example.

mko Over a year ago

Actually when value is null, JSON.stringify will not include this param in json output. So the solution is to create additional c# method something like public static int Insert(string name). This works

Johan Over a year ago

@John JSON.stringify inclues properties with null values. console.log(JSON.stringify({ "name": 'blah', "parentID": null }));

mko Over a year ago

try console.log(JSON.stringify({ "name": 'blah', "parentID": undefined})); i think it is up to jquery version

|

faby · Accepted Answer · 2014-06-09 12:35:48Z

0

Since you declared the parameter as nullable (in Insert function) you can safely do not send it from ajax function

$.ajax({
                type: "POST",
                url: "topic.aspx/Insert",
                data: JSON.stringify({
                    "name": name

                }),
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (msg) {


                },
                error: function (msg) { alert(msg.responseText); }


            });
            }

After this you'll see a null value in Insert function for parentID parameter

answered Jun 9, 2014 at 12:35

faby

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