C # ArrayList usage

The System. Collections. ArrayList class is a special array. By adding and deleting elements, You can dynamically change the length of the array.

I. Advantages

1. Supports automatic resizing.

2. Flexible element insertion

3. Flexible deletion of Elements

4. flexible access to elements

Ii. Limitations

Compared with the average array, the speed is lower.

3. Add Elements

1. public virtual int Add (object value );

Add the object to the end of ArrayList

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

Content is abcde

2. public virtual void Insert (int index, object value );

Insert the element to the specified index of ArrayList

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

AList. Insert (0, "aa ");

The result is aaabcde.

3. public virtual void InsertRange (int index, ICollectionc );

Insert an element in the set to the specified index of ArrayList.

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

ArrayList list2 = new ArrayList ();

List2.Add ("tt ");

List2.Add ("ttt ");

AList. InsertRange (2, list2 );

The result is abtttttcde.

Iv. Delete

A) public virtual void Remove (object obj );

Remove the first matching item of a specific object from the ArrayList. Note that it is the first

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

AList. Remove ("");

The result is bcde.

2. public virtual void RemoveAt (intindex );

Removes the element at the specified index of ArrayList.

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

AList. RemoveAt (0 );

The result is bcde.

3. public virtual void RemoveRange (int index, int count );

Remove a certain range of elements from the ArrayList. Index indicates the Index, and count indicates the number starting from the Index.

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

AList. RemoveRange (1, 3 );

The result is AE.

4. public virtual void Clear ();

Remove all elements from ArrayList.

5. Sorting

A) public virtual void Sort ();

Sorts the elements in an ArrayList or a part of it.

ArrayListaList = newArrayList ();

AList. Add ("e ");

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

DropDownList1.DataSource = aList; // DropDown ListDropDownList1;

DropDownList1.DataBind ();

The result is eabcd.

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

AList. Sort (); // Sort

DropDownList1.DataSource = aList; // DropDownListDropDownList1;

DropDownList1.DataBind ();

The result is abcde.

B) public virtual void Reverse ();

Reverses the order of elements in an ArrayList or a part of it.

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

AList. Reverse (); // Reverse

DropDownList1.DataSource = aList; // DropDownListDropDownList1;

DropDownList1.DataBind ();

The result is edcba.

6. Search

A) public virtual int IndexOf (object );

B) public virtual int IndexOf (object, int );

C) public virtual int IndexOf (object, int, int );

Returns the index starting from scratch for the first matching item of a value in the ArrayList or part of it. -1 is not found.

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");

AList. Add ("c ");

AList. Add ("d ");

AList. Add ("e ");

IntnIndex = aList. IndexOf ("a"); // 1

NIndex = aList. IndexOf ("p"); // not found,-1

D) public virtual int LastIndexOf (object );

E) public virtual int LastIndexOf (object, int );

F) public virtual int LastIndexOf (object, int, int );

Returns the index starting from scratch for the last matching item of a value in the ArrayList or part of it.

ArrayList aList = new ArrayList ();

AList. Add ("");

AList. Add ("B ");