in C# in LIST I am not able to assign a value

Question

Here request is the LIST with the "sortcolumns" property, so Initialy it "sortcolumns" is null so programmatically I am trying to assign a two values which are part of sort columns

request.SortColumns.Add( new SortColumn() { Name = "PolicyName", Direction = DirectionType.Descending });

I am always getting this error, please let me know why - Object reference not set to an instance of an object.

here

public class SortColumn
{
    public string Name { get; set; }
    public DirectionType Direction { get; set; }
}

Answer 1

You seemingly need to initialize the list before you start adding to it (once)

request.SortColumns = new List<SortColumn>();

This might be in the constructor of the request, it might be before you Add code, you might even make it a intialised property of the class itself

Example of Property Intialization

public class SomeRequest
{

   public List<SortColumn> SortColumns {get;set;} = new List<SortColumn>();

   ...

Example of Constructor Intializer

public class SomeRequest
{

   public SomeRequest()
   {

       SortColumns = new List<SortColumn>();
       ...

Answer 2

You need to initialise the property before you use it, try this:

request.SortColumns = new List<SortColumn>();
request.SortColumns.Add( new SortColumn() { Name = "PolicyName", Direction = DirectionType.Descending });