- Completely masking some of the properties

var example = new 
{
	SomeValue = "Demo",
	Password = "SomePasswordHere",
	DepthObject = new 
	{
		Password = "SomePasswordHere2",
		Card = new 
		{
			Number = "555500022223333"
		}
	},
	CreditCardNumber = "5555000011112222",
	Card = new 
	{
		Number = "555500022223333"
	}
};

var exampleAsString = JsonConvert.Serialize(example); // value must be a json string to masked

// note that password is only replaced when is in root path
var blacklist = new string[] { "password", "card.number", "*.card.number" "creditcardnumber" };
var mask = "******";

var maskedExampleAsString = exampleAsString.MaskFields(blacklist, mask);

Console.WriteLine(maskedExampleAsString);

- Partially masking some of the properties

var example = new 
{
	SomeValue = "Demo",
	Password = "SomePasswordHere",
	DepthObject = new 
	{
		Password = "SomePasswordHere2",
		Card = new 
		{
			Number = "555500022223333"
		}
	},
	CreditCardNumber = "5555000011112222",
	Card = new 
	{
		Number = "555500022223333"
	}
};

var blacklistPartial = new Dictionary<string, Func<string, string>>(StringComparer.OrdinalIgnoreCase) // The key is the property to be partially masked and the value is the function to be applied.
{
    { "*card.number", text =>  // Note that the property "*card.number" is also in the blacklist. If the property only exists in the blacklistPartial, it will not be masked.
        Regex.Replace(
            text,
            @"(\d{4,5})[ -|]?(\d{3,6})[ -|]?(\d{3,5})[ -|]?(\d{3,4})",
            match => $"{match.Value.Substring(0, 6)}*****{match.Value.Substring(match.Value.Length - 4, 4)}")
    }
};

var exampleAsString = JsonConvert.Serialize(example); // The value must be a JSON string to be masked.

// Note that the password is only replaced when it is in the root path.
var blacklist = new string[] { "password", "*card.number", "creditcardnumber" };
var mask = "******";

var maskedExampleAsString = exampleAsString.MaskFields(blacklist, mask, blacklistPartial); // The blacklistPartial is optional. If provided, it will apply the mask only if the property is also in the blacklist.

Console.WriteLine(maskedExampleAsString);