/*
A Programmer's Introduction to C# (Second Edition)
by Eric Gunnerson
Publisher: Apress L.P.
ISBN: 1-893115-62-3
*/
// 31 - InteropCalling Native DLL FunctionsCalling a Function with a Structure Parameter
// copyright 2000 Eric Gunnerson
using System;
using System.Runtime.InteropServices;
struct Point
{
public int x;
public int y;
public override string ToString()
{
return(String.Format("({0}, {1})", x, y));
}
}
struct Rect
{
public int left;
public int top;
public int right;
public int bottom;
public override string ToString()
{
return(String.Format("({0}, {1})
({2}, {3})", left, top, right, bottom));
}
}
struct WindowPlacement
{
public uint length;
public uint flags;
public uint showCmd;
public Point minPosition;
public Point maxPosition;
public Rect normalPosition;
public override string ToString()
{
return(String.Format("min, max, normal:
{0}
{1}
{2}",
minPosition, maxPosition, normalPosition));
}
}
public class CallingaFunctionwithaStructureParameterWindow
{
[DllImport("user32")]
static extern int GetForegroundWindow();
[DllImport("user32")]
static extern bool GetWindowPlacement(int handle, ref WindowPlacement wp);
public static void Main()
{
int window = GetForegroundWindow();
WindowPlacement wp = new WindowPlacement();
wp.length = (uint) Marshal.SizeOf(wp);
bool result = GetWindowPlacement(window, ref wp);
if (result)
{
Console.WriteLine(wp);
}
}
}
Class Interface
C# always creates a structure instance as a value-type variable even using the new operator
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
//
// ValType.cs -- Demonstrates that C# always creates a structure instance as
// a value-type variable even using the new operator.
// Compile this program using the following command line:
// C:>csc ValType.cs
//
namespace nsValType
{
using System;
public struct POINT
{
public int cx;
public int cy;
}
public class ValType
{
static public void Main()
{
POINT point1;
point1.cx = 42;
point1.cy = 56;
ModifyPoint (point1);
Console.WriteLine ("In Main() point2 = ({0}, {1})", point1.cx, point1.cy);
POINT point2 = new POINT ();
// point2.cx = 42;
// point2.cy = 56;
Console.WriteLine ();
ModifyPoint (point2);
Console.WriteLine ("In Main() point2 = ({0}, {1})", point2.cx, point2.cy);
}
static public void ModifyPoint (POINT pt)
{
pt.cx *= 2;
pt.cy *= 2;
Console.WriteLine ("In ModifyPoint() pt = ({0}, {1})", pt.cx, pt.cy);
}
}
}
Illustrates the use of a struct
/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
Example5_15.cs illustrates the use of a struct
*/
// declare the Rectangle struct
struct Rectangle
{
// declare the fields
public int Width;
public int Height;
// define a constructor
public Rectangle(int Width, int Height)
{
this.Width = Width;
this.Height = Height;
}
// define the Area() method
public int Area()
{
return Width * Height;
}
}
public class Example5_15
{
public static void Main()
{
// create an instance of a Rectangle
System.Console.WriteLine("Creating a Rectangle instance");
Rectangle myRectangle = new Rectangle(2, 3);
// display the values for the Rectangle instance
System.Console.WriteLine("myRectangle.Width = " + myRectangle.Width);
System.Console.WriteLine("myRectangle.Height = " + myRectangle.Height);
// call the Area() method of the Rectangle instance
System.Console.WriteLine("myRectangle.Area() = " + myRectangle.Area());
}
}
Issue an error message if you do not initialize all of the fields in a structure
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
//
// Struct.cs - Issue an error message if you do not initialize all of
// the fields in a structure
//
// Compile this program with the following command line:
// C:>csc Struct.cs
//
using System;
namespace nsStruct
{
struct POINT
{
public int cx;
public int cy;
public int var;
public override string ToString ()
{
return ("(" + cx + ", " + cy + ")");
}
}
public class StructDemo2
{
static public void Main ()
{
POINT pt;
pt.cx = 24;
pt.cy = 42;
Console.WriteLine (pt);
// Console.WriteLine ("(" + pt.cx + ", " + pt.cy + ")");
}
}
}
Demonstates assignment operator on structures and classes.
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
//
// CmpStCls.cs -- Demonstates assignment operator on structures and classes.
// Compile this program with the following command line:
// C:>csc CmpStCls.cs
//
namespace nsCompare
{
using System;
//
// Define a structure containing the x and y coordinates of a point
struct stPoint
{
public int cx;
public int cy;
}
//
// Define a class containing the x and y coordinates of a point
class clsPoint
{
public int cx;
public int cy;
}
public class CmpStCls
{
static public void Main ()
{
// Declare two structure variables
stPoint spt1, spt2;
// Initialize the members of only one structure
spt1.cx = 42;
spt1.cy = 24;
// Assign the first structure to the first
spt2 = spt1;
// Now modify the first structure
spt1.cx = 12;
spt1.cy = 18;
// Show the results
Console.WriteLine ("For structures:");
Console.WriteLine (" The point for spt1 is ({0}, {1})", spt1.cx, spt1.cy);
Console.WriteLine (" The point for spt2 is ({0}, {1})", spt2.cx, spt2.cy);
// Now do the same thing with instances of the class
clsPoint cpt1, cpt2;
cpt1 = new clsPoint();
// Initialize the members of only one class instance
cpt1.cx = 42;
cpt1.cy = 24;
// Assign the first class instance to the second
cpt2 = cpt1;
// Modify the first class
cpt1.cx = 12;
cpt2.cy = 18;
// Show the results
Console.WriteLine ("
For structures:");
Console.WriteLine (" The point for cpt1 is ({0}, {1})", cpt1.cx, cpt1.cy);
Console.WriteLine (" The point for cpt2 is ({0}, {1})", cpt2.cx, cpt2.cy);
}
}
}
demonstrates using a structure to return a group of variables from a function
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// tm.cs - demonstrates using a structure to return a group of variables
// from a function
//
// Compile this program using the following command line:
// D:>csc tm.cs
//
namespace nsStructure
{
using System;
using System.Globalization;
public struct tm
{
public int tm_sec; // Seconds after the minute
public int tm_min; // Minutes after the hour
public int tm_hour; // Hours since midnight
public int tm_mday; // The day of the month
public int tm_mon; // The month (January = 0)
public int tm_year; // The year (00 = 1900)
public int tm_wday; // The day of the week (Sunday = 0)
public int tm_yday; // The day of the year (Jan. 1 = 1)
public int tm_isdst; // Flag to indicate if DST is in effect
}
public class tmDemo
{
static public void Main()
{
DateTime timeVal = DateTime.Now;
tm tmNow = LocalTime (timeVal);
string strTime = AscTime (tmNow);
Console.WriteLine (strTime);
}
static public tm LocalTime(DateTime tmVal)
{
tm time;
time.tm_sec = tmVal.Second;
time.tm_min = tmVal.Minute;
time.tm_hour = tmVal.Hour;
time.tm_mday = tmVal.Day;
time.tm_mon = tmVal.Month - 1;
time.tm_year = tmVal.Year - 1900;
time.tm_wday = (int) tmVal.DayOfWeek;
time.tm_yday = tmVal.DayOfYear;
TimeZone tz = TimeZone.CurrentTimeZone;
time.tm_isdst = tz.IsDaylightSavingTime (tmVal) == true ? 1 : 0;
return (time);
}
//
// Returns a string representing a time using UNIX format
static public string AscTime (tm time)
{
const string wDays = "SunMonTueWedThuFriSat";
const string months = "JanFebMarAprMayJunJulAugSepOctNovDec";
string strTime = String.Format ("{0} {1} {2,2:00} " +
"{3,2:00}:{4,2:00}:{5,2:00} {6}
",
wDays.Substring (3 * time.tm_wday, 3),
months.Substring (3 * time.tm_mon, 3),
time.tm_mday, time.tm_hour,
time.tm_min, time.tm_sec, time.tm_year + 1900);
return (strTime);
}
}
}
Defining functions for structs
using System;
struct Dimensions {
public double Length;
public double Width;
Dimensions(double length, double width) { Length = length; Width = width; }
public double Diagonal {
get {
return Math.Sqrt(Length * Length + Width * Width);
}
}
}