1	C# Base Classes LA C#, SIG of LAFox.org August 6, 2002
2	Overview Various base classes will be described Examples showing use and performance of these classes will be presented Code examples and this presentation are posted on the web page http://www.vi-i.com/talks and on the web site http://www.lacsharp.org.
3	The fundamental System.Object base class and how its Equals method is used and overridden All classes are subclasses of System.Object Methods of System.Object ToString – string representation (for output display); by default the name of the object GetHashCode – gets a hash code so object can be looked up in a dictionary (integer value) Equals – returns .T. if current object’s “value” matches value object; used to find objects in collections ReferenceEquals – returns .T. if object is the same as argument object (exactly the same object; not just the same value) GetType – returns the type of the object in System.Type MemberwiseClone – copies to another object all data values
4	String Handling, string builder, and how strings are concatenated Basic String Methods: int.CompareTo(string2) [uses locale to distinguish chars] int=string1.CompareOrdinal(string2) [no locale used] int=string1.IndexOf(char), int=string1.IndexOf(substring) int=string1.IndexOfAny(char[]) int=string1.LastIndexOf(char), int=string1.LastIndexOf(substring) int=string1.LastIndexOfAny(char[]) string=string1.PadLeft(int), string=string1.PadLeft(int,char) string=string1.PadRight(int), string=string1.PadRight(int,char) string=string1.Replace(substring1,substring2) string[]=string1.Split(char) – split where char occurs into substrings string=string1.Substring(int offset,int length) [offset=0,1,…] string=string1.ToLower(), string=string1.ToUpper(), string=string1.Trim()
5	String Handling, continued StringBuilder – preallocates memory and appends string segments into that memory, much faster than repeated use of string=string+newString /* build string representing contents of a string[] array */ private string ArrayToString(string[] array) { StringBuilder Output=new StringBuilder(1000); int i; if (array.Length==0) return ""; for (i=0;i<array.Length;i++) Output.Append("\",\""+array[i].ToString()); return "("+Output.ToString().Substring(2)+"\")"; } Formatting values into strings: String.Format("Format {0,10:E} and {0,8:F} of pi and e:", System.Math.PI, System.Math.E);
6	Regular Expressions - classes and methods for implementing fast, complex string searches Search text in richTextBox1 on form using regular expression in textBox1, and show result by highlighting matches in bold font: MatchCollection Matches=Regex.Matches(richTextBox1.Text, textBox1.Text, RegexOptions.IgnoreCase \| RegexOptions.IgnorePatternWhitespace \| RegexOptions.ExplicitCapture); System.Drawing.Font currentFont = richTextBox1.SelectionFont; System.Drawing.FontStyle newFontStyle; newFontStyle = FontStyle.Bold; foreach (Match NextMatch in Matches) { this.richTextBox1.SelectionStart=NextMatch.Index; this.richTextBox1.SelectionLength=NextMatch.ToString().Length; richTextBox1.SelectionFont = new Font(currentFont.FontFamily, currentFont.Size, newFontStyle); };
7	Groups of Objects - Arrays, Array Lists, Collections, and Dictionaries Arrays int[] Array=new int[10000000]; int i; long sum; sum=0; for (i=0;i<10000000;i++) Array[i]=i+1; for (i=0;i<10000000;i++) sum=sum+Array[i]; MessageBox.Show("Sum(array[i]=i) from 1 to 1,000,000 = "+ sum.ToString(),"Array",MessageBoxButtons.OK, MessageBoxIcon.Information); ArrayLists ArrayList List=new ArrayList(100000); int i; long sum=0; for (i=0;i<int.Parse(this.textBox2.Text);i++) List.Add(i+1); MessageBox.Show("Created array list","Created Array List", MessageBoxButtons.OK, MessageBoxIcon.Information); for (i=0;i<List.Count;i++) sum=sum+(int)List[i]; MessageBox.Show("Sum(ArrayList) from 1 to "+ List.Count.ToString()+" = "+sum.ToString(),"Summed Array List", MessageBoxButtons.OK, MessageBoxIcon.Information);
8	Groups of Objects, continued Collections /* Create and sum integer sequence collection */ IntegerSequence Sequence=new IntegerSequence( int.Parse(textBox3.Text),int.Parse(textBox4.Text)); long sum=0; foreach (int Integer in Sequence) sum=sum+Integer; MessageBox.Show("Sum(integer sequence collection) from "+textBox3.Text.Trim()+" to "+textBox4.Text.Trim()+" = "+sum.ToString(), "Collection",MessageBoxButtons.OK, MessageBoxIcon.Information); public class IntegerSequence : IEnumerable { public int Start; public int End; public IntegerSequence(int Start, int End) {this.Start=Start; this.End=End;} public IEnumerator GetEnumerator() {return new SequenceCollection(this);} }
9	Groups of Objects: Collection enumerator class public class SequenceCollection : IEnumerator { IntegerSequence sequence; int index; public SequenceCollection(IntegerSequence Sequence) {sequence=Sequence; index=sequence.Start-1;} public bool MoveNext() {++index; return (index>sequence.End)?false:true;} public object Current{ get{ if (index<sequence.Start \| index>sequence.End) throw new InvalidOperationException( "The selected IntegerSequence object is out of range"); return index;} } public void Reset() {index=sequence.Start-1;} }
10	Groups of Objects: Dictionaries Dictionaries /* Create dictionary of squares and look up and sum entries / Hashtable Dictionary=new Hashtable(31); long i; long sum=0; int m=int.Parse(this.textBox5.Text); int n=int.Parse(this.textBox6.Text); for (i=m;i<=n;i++) Dictionary.Add(i,(ii)); MessageBox.Show("Created dictionary","Created Dictionary", MessageBoxButtons.OK,MessageBoxIcon.Information); for (i=m;i<=n;i++) sum=sum+(long)Dictionary[i]; MessageBox.Show("Sum(dictionary entry = n*n) from "+m.ToString()+ " to "+n.ToString()+" = "+sum.ToString(),"Summed Dictionary", MessageBoxButtons.OK, MessageBoxIcon.Information);
11	Reflection - classes that assign attributes to code that can be queried at build and at run time /* show type and methods of objects obj */ private string ShowType(object obj) { Type type=obj.GetType(); StringBuilder Output=new StringBuilder(1000); Output.Append("Type "+type.Name+" ("+type.FullName+")\nin "+ type.Namespace+"\n"); if (type.BaseType != null) Output.Append("Base type "+type.BaseType.Name+"\n"); if (type.UnderlyingSystemType != null) Output.Append( "Underlying system type "+type.UnderlyingSystemType.Name+"\n"); Output.Append("\nPublic Members:\n"); MemberInfo[] Members=type.GetMembers(); foreach (MemberInfo Member in Members) Output.Append(Member.DeclaringType+ " "+Member.MemberType+": "+Member.Name +"\n"); return Output.ToString(); }
12	Reflection, continued One can also create custom attributes that can be assigned to blocks of code, and methods that will display these attributes (e.g., author, date of last change, version number)
13	Threading - starting multiple execution threads, prioritorizing and synchronizing string Title; int form; void TestThreading { Title = this.Text; /* from form / int i; form=0; / with threading / for (i=0; i<n && i<5; i++) { Threads[i]=new Thread(new ThreadStart(StartWindow)); Threads[i].Start();} / without threadng */ for (i=0; i<n && i<5; i++) StartWindow(); } void StartWindow() { FormThreading aForm = new FormThreading(); aForm.Text = Title+":"+(form+1).ToString(); Forms[form++] = aForm; aForm.ShowDialog(); }
14	Performance of C# vs. VFP and ASP 1,000,000 string concatenations C#: 190 seconds C# with StringBuilder: 0.3 seconds VFP: 3 seconds ASP 2.0 (not ASP.NET): 7 seconds Sum i (i=1 to 1,000,000) C# array: 0.1 seconds (numbers stored) C# array list: 15 seconds (numbers stored) C# collection: 0.1 seconds (numbers generated by method calls) C# dictionary: 4 seconds (numbers stored) VFP code: 1.2 seconds (calculation; nothing stored) VFP build cursor and sum it: 4.5 seconds (numbers stored)