C# Online Compiler | .NET Fiddle

using System;
using System.Collections;
using System.Collections.Generic;

public interface ICommand
{
	void Execute();
}

public interface IUndoableCommand: ICommand
{
	void Unexecute();
}

public class Document
{
	public string Content {get; set;}
	public void MakeBold()
	{
		Content = "<b>" + Content + "</b>";
	}
}

public class BoldCommand: IUndoableCommand
{
	private Document document;
	private History history;
	private string prevContent;
	
	public BoldCommand(Document document, History history)
	{
		this.document= document;
		this.history = history;
	}
	
	public void Execute()
	{
		this.prevContent = document.Content;
		document.MakeBold();
		history.Push(this);
	}
	
	public void Unexecute()
	{
		document.Content = this.prevContent;
	}
}

public class UndoCommand: ICommand
{
	private History history;
	
	public UndoCommand(History history)
	{
		this.history = history;
	}

	public void Execute()
	{
		var command = history.Pop();
		command.Unexecute();
	}
}

public class History
{
	private Stack<IUndoableCommand> stack = new Stack<IUndoableCommand>();
	
	public void Push(IUndoableCommand command)
	{
		stack.Push(command);
	}
	
	public IUndoableCommand Pop()
	{
		return stack.Pop();
	}
}

public class Program
{
	public static void Main()
	{
		var history = new History();
		var document = new Document();
		document.Content = "Hello World";
		Console.WriteLine(document.Content);
		var command = new BoldCommand(document, history);
		command.Execute();
		Console.WriteLine(document.Content);
		
		var undoCommand = new UndoCommand(history);
		undoCommand.Execute();
		Console.WriteLine(document.Content);
	}
}

Cached Result

Environment version: 4.0.30319.42000
Json.NET version: Newtonsoft.Json, Version=10.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed

Testing conversion of Question49898782.KeyList to System.Data.DataTable.
Input JSON:
{ "ssid" : 1,
  "dim" : 2,
  "type" : 3,
  "list_of_business_keys":
  [
      {"business_key" : {"column_1" : 100, "column_2" : 1000}},
      {"business_key" : {"column_1" : 200, "column_2" : 1000}},
      {"business_key" : {"column_1" : 300, "column_2" : 1000}},
      {"business_key" : {"column_1" : 400, "column_2" : 1000}},
      {"business_key" : {"column_1" : 500, "column_2" : 1000}}
  ]
}
Output System.Data.DataTable:
[
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "column_1": 100,
    "column_2": 1000
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "column_1": 200,
    "column_2": 1000
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "column_1": 300,
    "column_2": 1000
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "column_1": 400,
    "column_2": 1000
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "column_1": 500,
    "column_2": 1000
  }
]

Testing conversion of Question49898782.KeyList to System.Data.DataTable.
Input JSON:
{ "ssid" : 1,
  "dim" : 2,
  "type" : 3,
  "list_of_business_keys":
  [
      {"business_key" : {"xxx" : "abc", "yyy" : 1000, "zzz" : 123}},
      {"business_key" : {"xxx" : "cde", "yyy" : 1000, "zzz" : 456}},
      {"business_key" : {"xxx" : "efg", "yyy" : 1000, "zzz" : 789}},
      {"business_key" : {"xxx" : "hij", "yyy" : 1000, "zzz" : 12 }},
      {"business_key" : {"xxx" : "klm", "yyy" : 1000, "zzz" : 345}}
  ]
}
Output System.Data.DataTable:
[
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "abc",
    "yyy": 1000,
    "zzz": 123
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "cde",
    "yyy": 1000,
    "zzz": 456
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "efg",
    "yyy": 1000,
    "zzz": 789
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "hij",
    "yyy": 1000,
    "zzz": 12
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "klm",
    "yyy": 1000,
    "zzz": 345
  }
]

Testing conversion of Question49898782.KeyList to System.Data.DataTable.
Input JSON:
{ "ssid" : 1,
  "dim" : 2,
  "type" : 3,
  "list_of_business_keys":
  [
      {"business_key" : {"xxx" : null, "yyy" : 1000, "zzz" : 123}},
      {"business_key" : {"xxx" : "row contains string-value cell that was initially null", "yyy" : 1000, "zzz" : 456}},
      {"business_key" : {"xxx" : "efg", "yyy" : 1000, "zzz" : 789}},
      {"business_key" : {"xxx" : "row contains floating point cell that was initially integral", "yyy" : 1000, "zzz" : 12.123 }},
      {"business_key" : {"added_property" : "added_value", "xxx" : "row contains string-valued cell that was initially integral", "yyy" : "1000", "zzz" : 345 }}
  ]
}
Output System.Data.DataTable:
[
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": null,
    "yyy": "1000",
    "zzz": 123.0,
    "added_property": null
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "row contains string-value cell that was initially null",
    "yyy": "1000",
    "zzz": 456.0,
    "added_property": null
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "efg",
    "yyy": "1000",
    "zzz": 789.0,
    "added_property": null
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "row contains floating point cell that was initially integral",
    "yyy": "1000",
    "zzz": 12.123,
    "added_property": null
  },
  {
    "ssid": 1,
    "dim": 2,
    "type": 3,
    "xxx": "row contains string-valued cell that was initially integral",
    "yyy": "1000",
    "zzz": 345.0,
    "added_property": "added_value"
  }
]

Done.