JsonConvert System.ArgumentNullException : 'Value cannot be null. Arg_ParamName_Name'

Question

Hi, I tried to do the tree view structure.
The code behind is

  public string TreeViewJSON { get; set; }  
  
        public void OnGet()  
        {  
            List<TreeViewNode> nodes = new List<TreeViewNode>();  
  
            //Loop and add the Parent Nodes.  
          foreach (FilePathP type in context.FilePathPs)  
          {  
                nodes.Add(new TreeViewNode { id = type.Id.ToString(), parent = "#",text = type.Name});  
  
          }  
  
            //Loop and add the Child Nodes.  
            foreach(FilePathP subtype in context.FilePathPs)  
            {  
                nodes.Add(new TreeViewNode { id = subtype.OrgLevel.ToString() + "-" + subtype.Id.ToString() ,  
                parent = subtype.OrgLevel.ToString(), text = subtype.Name});  
            }  
  
            // Serialize to JSON string.  
             this.TreeViewJSON = JsonConvert.SerializeObject(nodes);  
  
        }  
  
        public void OnPostSubmit(string selectedItems)  
        {  
            List<TreeViewNode> items = JsonConvert.DeserializeObject<List<TreeViewNode>>(selectedItems);  
        }  

The data come from the sql view

I received this message :
I don't understand why I received this message because the list not null.

Have you an idea about this message and how I can solve it?

one thing that is disturbing is that I have the node counter set to 68 and it displays null values from [68] to [127]

Answer 1

I have not changed my code. (I forgot a virgule) I still get the same result as my first post.

The value selectedItems return always a status 500. I don't know how solve it?

t seems you simply do not have the skill set to write web applications.

FYI I make do with my own means. I don't want to be an expert, but I need experts to help me.

Answer 2

I've applied the structure of your example code and I've always the issue

I can't give you selectedItems because in dev tools console I received it

Answer 3

we would need the TreeViewNode class definition, and the simplest selectedItems string that causes the error.

note: it odd you call it a TreeViewNode class and load from a hierarchical source, but create a flat list.

Answer 4

Here the model class of TreeViewNode

 public string id { get; set; }  
        public string parent { get; set; }  
        public string text { get; set; }  

I use the jQuery jsTree in HTML Razor Page.

<div id="jstree"></div>  
                                            <form method="post">  
                                                <input type="hidden" name="selectedItems" id="selectedItems" />  
                                                <input type="submit" value="Submit" asp-page-handler="Submit" />  
                                            </form>  
         <script type="text/javascript">  
                                                        $(function () {  
                                                            $('#jstree').on('changed.jstree', function (e, data) {  
                                                                var i, j;  
                                                                var selectedItems = [];  
                                                                for(i = 0, j = data.selected.length; i < j; i++) {      
                                                                    var id = data.selected[i];  
                                                                    if(id.indexOf('-') != -1){  
                                                                        id = id.split("-")[1];  
                                                                    }  
                                                                    selectedItems.push({  
                                                                        text: data.instance.get_node(data.selected[i]).text,  
                                                                        id: id,  
                                                                        parent: data.node.parents[0]  
                                                                    });  
                                                                }  
                                                            $('#selectedItems').val(JSON.stringify(selectedItems));  
                                                            }).jstree({  
                                                                        "core": {  
                                                                            "themes": {  
                                                                                "variant": "large"  
                                                                            },  
                                                                            "data": @Html.Raw(Model.TreeViewJSON)  
                                                                        },  
                                                                        "checkbox": {  
                                                                            "keep_selected_style": false  
                                                                        },  
                                                                        "plugins": ["wholerow", "checkbox"],                                                                     
                                                            });  
                                                        });  
  

Answer 5

You should show the selectedItems postback text.