Question

I write an asp.net MVC controler

I send JSON to the client as a response to an action.

{ A : "bla", B: "bla2"}

How can I make field B tentative acorrding to existance of its value

meaning:
Server object like

{ A : "bla", B:  null}

will be sent as

{ A : "bla"}

Answer 1

This link might help http://ftp.java2s.com/Code/CSharp/Network/RemovesJsonnullobjectsfromtheserializedstringandreturnanewstringExtentionMethod.htm

Basically you serialize the c# object to a json, then you can use a regex to find all properties with null value and remove them

EDIT:

You can have an extention method on string like so

public static string RemoveJsonNulls(this string str)
    {
        if (!str.IsEmptyOrNull())
        {
            Regex regex = new Regex(UtilityRegExp.JsonNullRegEx);
            string data = regex.Replace(str, string.Empty);
            regex = new Regex(UtilityRegExp.JsonNullArrayRegEx);
            return regex.Replace(data, "[]");
        }
        return null;
    }

public static string JsonNullRegEx = "[\"][a-zA-Z0-9_]*[\"]:null[ ]*[,]?";

public static string JsonNullArrayRegEx = "\\[( *null *,? *)*]";