Why can't my IList implementation be used as a dataSource

Question

I want to bind my object taskCollection to my checkListBox. taskCollection implements the interface IList<Task>.

When I try to use it as a data source I get the error

System.ArgumentException : Complex DataBinding accepts as a data source either an IList or an IListSource.

Here is my TaskCollection:

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

namespace CLBatchGUI
{
    /// <summary>
    /// Description of TaskCollection.
    /// </summary>
    public class TaskCollection:IList<Task>
    {
        private List<Task> _tasks;

        public TaskCollection()
        {
            _tasks = new List<Task>();
        }

        public void executeTasks(){
        }

        public static void loadFromCSV(string path){
        }

        public void saveToCSV(string path){
            StreamWriter sw= new StreamWriter(path);
            saveToCSV(sw);
        }

        public void saveToCSV(TextWriter sw){
            if(_tasks.Count==0)
                throw new ApplicationException("There are no tasks to save");
            foreach (var Task in _tasks) {
                Task.validate();
            }

            try{
                sw.Write("TaskName,");
                for(int i=0;i<_tasks[0].job.parameters.Count;i++){
                    sw.Write(_tasks[0].job.parameters[i].Name);
                    if(i==_tasks.Count-1)
                        sw.Write("\n");
                    else
                        sw.Write(",");
                }
                for(int i=0;i<_tasks.Count;i++){
                    sw.Write(_tasks[i].Name +",");
                    for(int n=0;n<_tasks[i].job.parameters.Count;n++){
                        sw.Write(_tasks[i].job.parameters[n].Text);
                        if(n==_tasks[i].job.parameters.Count-1)
                            sw.Write("\n");
                        else
                            sw.Write(",");
                    }


                }
            }catch(Exception ex){
                throw new ApplicationException(ex.Message);
            }

        }

        public Task this[int index]{
            get{
                return _tasks[index];
            }
            set{
                _tasks[index]=value;
            }
        }

        public int Count {
            get {
                return _tasks.Count;
            }
        }

        public bool IsReadOnly {
            get {
                return false;
            }
        }

        public int IndexOf(Task item)
        {
            return _tasks.IndexOf(item);
        }

        public void Insert(int index, Task item)
        {
            _tasks.Insert(index,item);
        }

        public void RemoveAt(int index)
        {
            _tasks.RemoveAt(index);
        }

        public void Add(Task item)
        {
            _tasks.Add(item);
        }

        public void Clear()
        {
            _tasks.Clear();
        }

        public bool Contains(Task item)
        {
            return _tasks.Contains(item);
        }

        public void CopyTo(Task[] array, int arrayIndex)
        {
            _tasks.CopyTo(array,arrayIndex);
        }

        public bool Remove(Task item)
        {
            return _tasks.Remove(item);
        }

        public IEnumerator<Task> GetEnumerator()
        {
            return _tasks.GetEnumerator();
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return _tasks.GetEnumerator();
        }
    }
}

Updated class:

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

 namespace CLBatchGUI
 {
/// <summary>
/// Description of TaskCollection.
/// </summary>
public class TaskCollection:IList<Task>,IList
{
    private List<Task> _tasks;
    public TaskCollection()
    {
        _tasks= new List<Task>();
    }

    public void executeTasks(){
    }

    public static void loadFromCSV(string path){

    }

    public void saveToCSV(string path){
        StreamWriter sw= new StreamWriter(path);
        saveToCSV(sw);
    }

    public void saveToCSV(TextWriter sw){
        if(_tasks.Count==0)
            throw new ApplicationException("There are no tasks to save");
        foreach (var Task in _tasks) {
            Task.validate();
        }

        try{
            sw.Write("TaskName,");
            for(int i=0;i<_tasks[0].job.parameters.Count;i++){
                sw.Write(_tasks[0].job.parameters[i].Name);
                if(i==_tasks.Count-1)
                    sw.Write("\n");
                else
                    sw.Write(",");
            }
            for(int i=0;i<_tasks.Count;i++){
                sw.Write(_tasks[i].Name +",");
                for(int n=0;n<_tasks[i].job.parameters.Count;n++){
                    sw.Write(_tasks[i].job.parameters[n].Text);
                    if(n==_tasks[i].job.parameters.Count-1)
                        sw.Write("\n");
                    else
                        sw.Write(",");
                }
            }
        }catch(Exception ex){
            throw new ApplicationException(ex.Message);
        }
    }

    public object this[int index]{
        get{
            return _tasks[index];
        }
        set{
            _tasks[index]=value;
        }
    }

    int IList.Count {
        get {
            return _tasks.Count;
        }
    }

    bool IList.IsReadOnly {
        get {
            return false;
        }
    }

    int IList.IndexOf(object item)
    {
        return _tasks.IndexOf(item);
    }

    void IList.Insert(int index, object item)
    {
        _tasks.Insert(index,item);
    }

    void IList.RemoveAt(int index)
    {
        _tasks.RemoveAt(index);
    }

    void IList.Add(object item)
    {
        _tasks.Add(item);
    }

    void IList.Clear()
    {
        _tasks.Clear();
    }

    bool IList.Contains(object item)
    {
        return _tasks.Contains(item);
    }

    void IList.CopyTo(object[] array, int arrayIndex)
    {
        _tasks.CopyTo(array,arrayIndex);
    }

    bool IList.Remove(object item)
    {
        return _tasks.Remove(item);
    }

 //     IList.IEnumerator<object> GetEnumerator()
 //     {
 //         return _tasks.GetEnumerator();
 //     }

 //     System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
 //     {
 //         return _tasks.GetEnumerator();
 //     }
}
 }

Answer 1

Your class has to implement IList or IListSource, as the error message tells you.

The class you postet implements IList<T>, but not IList.

So you have to implement IList yourself. You can do it explicitly, so you can't accidently add an object that is not a Task (since the non-generic Add method will be hidden), as long as you don't explicitly cast your TaskCollection to IList and call the non-generic Add method.

public class TaskCollection : IList<Task>, IList
{
    int IList.Add(object value)
    {
        // just call the generic version
        Add((Task)value);
    }

    int IList.IndexOf(object value)
    {
        // just call the generic version
        return IndexOf((Task)value);
    }

    ...
}