could you please see the code.i made the code.but when at home.cshtml wants to call.comes an error .(System.NullReferenceException: "Object reference not set to an instance of an object.").

------------------------convert_code----------

 public class MyLookAlikeArchetypeFieldSet
    {

[JsonProperty("nam")]
public string Nam { get; set; }

[JsonProperty("valu")]
public string Valu { get; set; }
}

public class MyLookAlikeArchetypeModel
{
    private List<MyLookAlikeArchetypeFieldSet> _Items;

public MyLookAlikeArchetypeModel()
{
    _Items = new List<MyLookAlikeArchetypeFieldSet>();
}

public MyLookAlikeArchetypeModel(List<MyLookAlikeArchetypeFieldSet> list)
{
    _Items = list;
}

public IEnumerator<MyLookAlikeArchetypeFieldSet> GetEnumerator()
{
    return _Items.GetEnumerator();
}



   public bool Any()
    {
        return _Items.Any();
    }

}

namespace MyConverters
{
    public class ContentPickerPropertyConverter : IPropertyValueConverter
    {
        private readonly IPublishedSnapshotAccessor _publishedSnapshotAccessor;
    //Injecting the PublishedSnapshotAccessor for fetching content
    public ContentPickerPropertyConverter(IPublishedSnapshotAccessor publishedSnapshotAccessor)
    {
        _publishedSnapshotAccessor = publishedSnapshotAccessor;
    }

    public bool IsConverter(IPublishedPropertyType propertyType)
    {
        return propertyType.EditorAlias=="Mypropretyeditor";
    }

    public bool? IsValue(object value, PropertyValueLevel level)
    {
        switch (level)
        {
            case PropertyValueLevel.Source:
                return value != null && (!(value is string) || string.IsNullOrWhiteSpace((string)value) == false);
            default:
                throw new NotSupportedException($"Invalid level: {level}.");
        }
    }

    public Type GetPropertyValueType(IPublishedPropertyType propertyType)
    {
        return typeof(IPublishedContent);
    }

    public PropertyCacheLevel GetPropertyCacheLevel(IPublishedPropertyType propertyType)
    {
        return PropertyCacheLevel.Elements;
    }

    public object ConvertSourceToIntermediate(IPublishedElement owner, IPublishedPropertyType propertyType, object source, bool preview)
    {
        if (source == null) return null;

        var attemptConvertInt = source.TryConvertTo<int>();
        if (attemptConvertInt.Success)
            return attemptConvertInt.Result;

        var attemptConvertUdi = source.TryConvertTo<Udi>();
        if (attemptConvertUdi.Success)
            return attemptConvertUdi.Result;

        return null;
    }

    public object ConvertIntermediateToObject(IPublishedElement owner, IPublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, object inter, bool preview)
    {
        if (inter == null)
            return null;

        if ((propertyType.Alias != null) == false)
        {
            IPublishedContent content;
            if (inter is int id)
            {
                content = _publishedSnapshotAccessor.PublishedSnapshot.Content.GetById(id);
                if (content != null)
                    return content;
            }
            else
            {
                var udi = inter as GuidUdi;
                if (udi == null)
                    return null;
                content = _publishedSnapshotAccessor.PublishedSnapshot.Content.GetById(udi.Guid);
                if (content != null && content.ContentType.ItemType == PublishedItemType.Content)
                    return content;
            }
        }

        return inter;
    }
    public object ConvertSourceToObject(PublishedPropertyType propertyType, object source, bool preview)
    {
        try
        {
            var list = JsonConvert.DeserializeObject<List<MyLookAlikeArchetypeFieldSet>>(source as string);
            return new MyLookAlikeArchetypeModel(list);
        }
        catch
        {
            return new MyLookAlikeArchetypeModel();
        }
    }
    public object ConvertIntermediateToXPath(IPublishedElement owner, IPublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, object inter, bool preview)
    {
        if (inter == null) return null;
        return inter.ToString();
    }
    }
}

-------------------------------javascript_code--

angular.module("umbraco").controller("MypropertyeditorControll", function ($scope) {
    $scope.init = function () {
       // alert("Der Controller ist gelandet");
        if ($scope.model.value === undefined || $scope.model.value === "") {
            $scope.model.value = {};
        }
    }

});

----------------------manifest_code

{

    propertyEditors: 
    [ 
        {  
            alias: "Mypropretyeditor",

            name: "My proprety editorE",

            icon: "icon-smiley-inverted",

            group: "media",

            editor: { 

                view:"~/App_Plugins/MarkDownEditor/Myproprety.html" ,
                valueType :"JSON"

            }

        } 
    ],  
    javascript : ['~/App_Plugins/MarkDownEditor/JS/Mypropretyeditor.controlle.js' 
    ],  
    css : ['~/App_Plugins/MarkDownEditor/CSS/Mypropretyeditor.Style.css' 
    ]  
}

----------------------------htmlproprety_code

<div ng-controller="MypropertyeditorControll" ng-init="init()">

    <input type="text" ng-model="model.value.object.key1" />
    <input type="text" ng-model="model.value.object.key2" />

</div>

---------------homehtml_code-----------

@{
    Layout = null;
    //Url.GetCropUrl(mediaItem: Model.Image, cropAlias: "Grid"​, htmlEncode: true);
    var obj = Model.Value<MyLookAlikeArchetypeModel>("Mypropretyeditor");

}

 <div>@foreach(var item in obj)
        {
        <p>@item.Nam</p>
        <p>@item.Valu</p>
        }</div>