Hi guys.
I'm using this article as a reference to use custom collection in propertygrid:
LINK
When I open the collectioneditor and remove all items then I press OK, I get an exception if null.
How can i solve that ?
I am using:
public T this[int index]
{
get
{
if (List.Count == 0)
{
return default(T);
}
else
{
return (T)this.List[index];
}
}
}
as a getter for an item, of course if I have no object how can i restart the whole collection ?
this is the whole code
/// <summary>
/// A generic folder settings collection to use in a property grid.
/// </summary>
/// <typeparam name="T">can be import or export folder settings.</typeparam>
[Serializable]
[TypeConverter(typeof(FolderSettingsCollectionConverter)), Editor(typeof(FolderSettingsCollectionEditor), typeof(UITypeEditor))]
public class FolderSettingsCollection_New<T> : CollectionBase, ICustomTypeDescriptor
{
private bool m_bRestrictNumberOfItems;
private int m_bNumberOfItems;
private Dictionary<string, int> m_UID2Idx = new Dictionary<string, int>();
private T[] arrTmp;
/// <summary>
/// C'tor, can determine the number of objects to
hold.
/// </summary>
/// <param name="bRestrictNumberOfItems">restrict the number of folders to
hold.</param>
/// <param name="iNumberOfItems">The number of folders to
hold.</param>
public FolderSettingsCollection_New(bool bRestrictNumberOfItems = false , int iNumberOfItems = 1)
{
m_bRestrictNumberOfItems = bRestrictNumberOfItems;
m_bNumberOfItems = iNumberOfItems;
}
/// <summary>
/// Add folder to collection.
/// </summary>
/// <param name="t">Folder to add.</param>
public void Add(T t)
{
if (m_bRestrictNumberOfItems)
{
if (this.List.Count >= m_bNumberOfItems)
{
return;
}
}
int index = this.List.Add(t);
if (t is WriteDataFolderSettings || t is ReadDataFolderSettings)
{
FolderSettingsBase tmp = t as FolderSettingsBase;
m_UID2Idx.Add(tmp.UID, index);
}
}
/// <summary>
/// Remove folder to collection.
/// </summary>
/// <param name="t">Folder to remove.</param>
public void Remove(T t)
{
this.List.Remove(t);
if (t is WriteDataFolderSettings || t is ReadDataFolderSettings)
{
FolderSettingsBase tmp = t as FolderSettingsBase;
m_UID2Idx.Remove(tmp.UID);
}
}
/// <summary>
/// Gets ot sets a folder.
/// </summary>
/// <param name="index">The index of the folder in the collection.</param>
/// <returns>A folder object.</returns>
public T this[int index]
{
get
{
//if (List.Count == 0)
//{
// return default(T);
//}
//else
//{
return (T)this.List[index];
//}
}
}
/// <summary>
/// Gets or sets a folder.
/// </summary>
/// <param name="sUID">The UID of the folder.</param>
/// <returns>A folder object.</returns>
public T this[string sUID]
{
get
{
if (this.Count == 0 || !m_UID2Idx.ContainsKey(sUID))
{
return default(T);
}
else
{
return (T)this.List[m_UID2Idx[sUID]];
}
}
}
/// <summary>
///
/// </summary>
/// <param name="sUID"></param>
/// <returns></returns>
public bool ContainsItemByUID(string sUID)
{
return m_UID2Idx.ContainsKey(sUID);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public String GetClassName()
{
return TypeDescriptor.GetClassName(this, true);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public AttributeCollection GetAttributes()
{
return TypeDescriptor.GetAttributes(this, true);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public String GetComponentName()
{
return TypeDescriptor.GetComponentName(this, true);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public TypeConverter GetConverter()
{
return TypeDescriptor.GetConverter(this, true);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public EventDescriptor GetDefaultEvent()
{
return TypeDescriptor.GetDefaultEvent(this, true);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public PropertyDescriptor GetDefaultProperty()
{
return TypeDescriptor.GetDefaultProperty(this, true);
}
/// <summary>
///
/// </summary>
/// <param name="editorBaseType"></param>
/// <returns></returns>
public object GetEditor(Type editorBaseType)
{
return TypeDescriptor.GetEditor(this, editorBaseType, true);
}
/// <summary>
///
/// </summary>
/// <param name="attributes"></param>
/// <returns></returns>
public EventDescriptorCollection GetEvents(Attribute[] attributes)
{
return TypeDescriptor.GetEvents(this, attributes, true);
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public EventDescriptorCollection GetEvents()
{
return TypeDescriptor.GetEvents(this, true);
}
/// <summary>
///
/// </summary>
/// <param name="pd"></param>
/// <returns></returns>
public object GetPropertyOwner(PropertyDescriptor pd)
{
return this;
}
/// <summary>
///
/// </summary>
/// <param name="attributes"></param>
/// <returns></returns>
public PropertyDescriptorCollection GetProperties(Attribute[] attributes)
{
return GetProperties();
}
/// <summary>
/// Called to get the properties of this type.
/// </summary>
/// <returns></returns>
public PropertyDescriptorCollection GetProperties()
{
// Create a collection object to
hold property descriptors
PropertyDescriptorCollection pds = new PropertyDescriptorCollection(null);
// Iterate the list of employees
for (int i = 0; i < this.List.Count; i++)
{
// Create a property descriptor for the employee item and add to the property descriptor collection
CollectionPropertyDescriptor_New<T> pd = new CollectionPropertyDescriptor_New<T>(this, i);
pds.Add(pd);
}
// return the property descriptor collection
return pds;
}
public T[] ToArray()
{
if (arrTmp == null)
{
arrTmp = new T[List.Count];
for (int i = 0; i < List.Count; i++)
{
arrTmp[i] = (T)List[i];
}
}
return arrTmp;
}
}
/// <summary>
/// Enable to display data about a collection in a property grid.
/// </summary>
/// <typeparam name="T">Folder object.</typeparam>
public class CollectionPropertyDescriptor_New<T> : PropertyDescriptor
{
private FolderSettingsCollection_New<T> collection = null;
private int index = -1;
/// <summary>
///
/// </summary>
/// <param name="coll"></param>
/// <param name="idx"></param>
public CollectionPropertyDescriptor_New(FolderSettingsCollection_New<T> coll, int idx) : base("#" + idx.ToString(), null)
{
this.collection = coll;
this.index = idx;
}
/// <summary>
///
/// </summary>
public override AttributeCollection Attributes
{
get
{
return new AttributeCollection(null);
}
}
/// <summary>
///
/// </summary>
/// <param name="component"></param>
/// <returns></returns>
public override bool CanResetValue(object component)
{
return true;
}
/// <summary>
///
/// </summary>
public override Type ComponentType
{
get
{
return this.collection.GetType();
}
}
/// <summary>
///
/// </summary>
public override string DisplayName
{
get
{
if (this.collection[index] != null)
{
return this.collection[index].ToString();
}
else
{
return null;
}
}
}
public override string Description
{
get
{
return "";
}
}
/// <summary>
///
/// </summary>
/// <param name="component"></param>
/// <returns></returns>
public override object GetValue(object component)
{
if (this.collection[index] != null)
{
return this.collection[index];
}
else
{
return null;
}
}
/// <summary>
///
/// </summary>
public override bool IsReadOnly
{
get { return false; }
}
public override string Name
{
get { return "#" + index.ToString(); }
}
/// <summary>
///
/// </summary>
public override Type PropertyType
{
get { return this.collection[index].GetType(); }
}
public override void ResetValue(object component)
{
}
/// <summary>
///
/// </summary>
/// <param name="component"></param>
/// <returns></returns>
public override bool ShouldSerializeValue(object component)
{
return true;
}
/// <summary>
///
/// </summary>
/// <param name="component"></param>
/// <param name="value"></param>
public override void SetValue(object component, object value)
{
// this.collection[index] = value;
}
}
