Converting objects into JSON and using the StringBuilder

Question

In my scenario I have list of object in C# code and need to be converted into JavaScript object. But there are certain condition, where the value of the object might be dynamic based on certain key.

I have a following method which will return string as JavaScript Object.

public string ItemToJson()
{
    List < Item > itemObj = GetItemList();
    if (itemObj.Count > 0)
    {
        StringBuilder sbObj = new StringBuilder();
        sbObj.Append("<script> let Items = {");
        var len = itemObj.Count;
        for (int i = 0; i < len; i++)
        {
            sbObj.Append(itemObj[i].Key);
            sbObj.Append(": { placeholder : \" ");
            sbObj.Append(itemObj[i].Placeholder);
            sbObj.Append(" \" , value : \" ");
            if (itemObj[i].Key == "Photo")
            {
                sbObj.Append(GetImage());
            }
            else
            {
                sbObj.Append(itemObj[i].Value);
            }
            sbObj.Append(" \" } ");
            if (i < len - 1)
                sbObj.Append(",");
        }
        sbObj.Append("} </script>");
        return sbObj.ToString();
    }
    else
    {
        return string.Empty;
    }
}

Here is the complete code of working console app.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace String_Builder_Demo
{
    class Program
    {
        public List<Item> GetItemList()
        {
            List<Item> items = new List<Item>
            {
                new Item(){ Key = "FirstName", Placeholder = "##FirstName##", Value="John" },
                new Item(){ Key = "LastName", Placeholder = "##LastName##", Value="Doe"},
                new Item(){ Key = "Email", Placeholder = "##Email##", Value="[email protected] " },
                new Item(){ Key = "Address", Placeholder = "##Address##", Value="Kathmandu" },
                new Item(){ Key = "Photo", Placeholder = "##Photo##", Value=""}
            };
            return items;
        }

        public string GetImage()
        {
            return "http://via.placeholder.com/350x150";
        }


        static void Main(string[] args)
        {
            Program obj = new Program();
            Console.WriteLine(obj.ItemToJson());
            Console.ReadLine();
        }

        public string ItemToJson()
        {
            List<Item> itemObj = GetItemList();
            if (itemObj.Count > 0)
            {
                StringBuilder sbObj = new StringBuilder();
                sbObj.Append("<script> let Items = {");
                var len = itemObj.Count;
                for (int i = 0; i < len; i++)
                {
                    sbObj.Append(itemObj[i].Key);
                    sbObj.Append(": { placeholder : \" ");
                    sbObj.Append(itemObj[i].Placeholder);
                    sbObj.Append(" \" , value : \" ");
                    if (itemObj[i].Key == "Photo")
                    {
                        sbObj.Append(GetImage());
                    }
                    else
                    {
                        sbObj.Append(itemObj[i].Value);
                    }
                    sbObj.Append(" \" } ");
                    if (i < len - 1)
                        sbObj.Append(",");
                }
                sbObj.Append("} </script>");
                return sbObj.ToString();
            }
            else
            {
                return string.Empty;
            }
        }
    }
    public class Item
    {
        public string Placeholder { get; set; }
        public string Value { get; set; }
        public string Key { get; set; }
    }
}

The above mention code will return following string.

<script>
    let Items = {
        FirstName:
        {
            placeholder: " ##FirstName## ",
            value: " John "
        },
        LastName:
        {
            placeholder: " ##LastName## ",
            value: " Doe "
        },
        Email:
        {
            placeholder: " ##Email## ",
            value: " [email protected]  "
        },
        Address:
        {
            placeholder: " ##Address## ",
            value: " Kathmandu "
        },
        Photo:
        {
            placeholder: " ##Photo## ",
            value: " http://via.placeholder.com/350x150 "
        }
    }
</script>

How can I optimize the above code and eliminate the if else condition from ItemToJson() method?

Answer 1

This is a bit off topic... but unless you are pushing a lot of data through this, StringBuilder isn't going to save you much.

Probably worth profiling to see. If you don't need it, then you can make the code pretty simple.

public string ItemToJson()
{
    List<Item> itemObj = GetItemList();
    if ( itemObj.Count <= 0 )
    {
        return string.Empty;
    }

    var parts = itemObj.Select (
        ( item ) =>
        {
            var val = item.Key == "Photo" ? GetImage () : item.Value;
            return $"{item.Key}: {{ placeholder : \" {item.Placeholder} \" , value : \" {val} \" }} ";
        } );

    var json = string.Join ( "," , parts);

    return $"<script> let Items = {{{json}}} </script>";
}

Answer 2

I'd recommend using a library for something like this. Formatting JSON manually difficult and error prone. Json.NET is nice and straight forward in this case.

public string ItemToJson()
{
    var result = new JObject();

    foreach (var property in GetItemList())
    {
        result.Add(property.Key, new JObject
        {
            ["placeholder"] = property.Placeholder,
            ["value"] = property.Key != "Photo"
                ? property.Value
                : "http://via.placeholder.com/350x150"
        });
    }

    return $"<script>let Items = {JsonConvert.SerializeObject(result)};</script>";
}

Answer 3

Had to put it here as it was getting too big for comment.

You definitely need to evaluate that condition based on code you have posted. So, the if/else construct is fine. Alternate options will need you to split the list into separate ones which will be more costly operations.

If I really have to nitpick, I would change the key datatype to int or add another property in Item class itself which is a bool. Perhaps something of is this sort:

class Item
{
    private string _key;
    public string Key
    {
        get
        {
            return _key;
        }

        set
        {
            _key = value;
            IsPhoto = (string.Compare(value, "Photo", true) == 0);
        }
    }

    public bool IsPhoto
    {
        get;
        set;
    }
}

This will remove the string comparison in loop and move it to object creation/update action.