C# More Classes and Controls

C# More Classes and Controls

TrackBar control

The Trackbar control provides a way to adjust a numeric setting using a mouse. It is sometimes also called a "slider". We have a short line marked with tick points and an indicator we can move left or tight using the mouse.

The properties of TrackBar include:

Value, an integer.
Maximum, an integer. The default value is 10. This corresponds to the right end of the line.
Minimum, an integer. The default value is 0. This corresponds to the left end of the line.
TickFrequency, an integer. The default value is 1. This tells us the difference in Value when we move from one tick to the next. The number of ticks displayed reflects this. The default thus is 10 ticks worth 1 each.

Process class

The Process class is used to start a new process, that is, a new running application. It has a large number of properties and methods. We shall look at only a few.

While there are constructors, a common way to start a process is to use a static method:

     Process.Start(String FileName);

where FileName is the name (and perhaps the path) of the application desired. This is similar to typing the name in the Run dialog box of the Windows Start menu.

Thus we might have:

     Process.Start("IExplore.exe");

to launch Internet Explorer.

An alternative is to provide command-line parameters as well:

     Process.Start(String FileName, String Parameter);

We might have:

     Process.Start("IExplore.exe", "www.cs.niu.edu");

The Process class can also be used by creating a Process instance, supplying information as the values of properties, and then simply using Start() (which, with no parameters, is not static). This is more flexible. We have access to properties such as:

StartInfo, an instance of the ProcessStartInfo class, which includes information such as the filename
ExitCode, an integer, the value returned by the application when it exits
StartTime, the time when the application started
ExitTime, the time when the application ended

MonthCalendar Control

The MonthCalendar control provides a calendar in the form for one or more months. The user can scroll forward and backward through the months.

It is possible to provide a list of dates to be displayed in bold type. There are properties to affect the appearance: font, size, colors, etc.

DateTimePicker Control

The DateTimePicker control allows a user to select a date and time. It displays the current date (by default) and has a drop-down option to produce a monthly calendar to select a different date.

Two of the properties are Value and Text. The relationship between these is the CustomFormat property. The value of the Text property is what we have when the CustomFormat (a string indicating what we want) is applied to Value. For instance, if the Value property is set to 06/01/2001 12:00:00 AM and the CustomFormat property is set to "dddd, MMMM dd, yyyy", the Text property value will be "Friday, June 01, 2001".

NumericUpDown Control

The NumericUpDown control is also known as a "spin box". It displays a numeric value with a pair of up/down arrows that allow the user to increase or decrease the value.

Some of the NumericUpDown's properties are:

Maximum, of type decimal, the maximum value allowed. The default is 100.
Minimum, of type decimal, the minimum value allowed. The default is 0.
Value, of type decimal, the current value displayed.
ReadOnly, of type bool. If this is true, the value can be changed only with the up and down arrows, not by typing a value into the box.

Of course, there are also properties for the size, position, font, color scheme, etc.

The most useful event associated with a NumericUpDown control is ValueChanged.

CheckBox Control

The CheckBox control is used to give the user a choice of two options such as on/off or true/false. It is in some sense a relative of a Button.

The most useful property of a CheckBox is Text, a string. This is displayed on the control, and we have reset it as needed.

The most useful event associated with a CheckBox is CheckedChanged.

Of course, there are also properties for the size, position, font, color scheme, etc.

ColorDialog class

The ColorDialog class provides a way for the user to choose a color which is then available as the Color property of the ColorDialog class. Normally it is created on the fly:

     ColorDialog MyDialog = new ColorDialog();

and we set some of its properties. A color-picking dialog box pops up, the users uses it, and it goes away.

Two of the properties are:

Color, of type Color. This is the color selected by the user.
ShowHelp, of type bool. If this is true, the dialog box includes a Help button. If pressed, the Help button raised a HelpRequest event.

OpenFileDialog Class

The OpenFileDialog class provides a dialog box that allows a user to check on whether a file exists and to open it. The user can type in a filename to search for or browse to find a filename.

Properties include:

InitialDirectory, of type String. This indicates where to start searching for a file. (It must be set to some value.)
CheckFileExists, of type bool. If this is true, a warning is dislayed if the user specifies a name that does not exist. The default is true.
CheckPathExists, of type bool. This is similar but involves a path that does not exit. The default is true.
FileName, of type String. This is the filename that is selected (get or set), including the extension.
FileNames, an array of String. This is similar but for multiple selected names.
SafeFileName, of type String. This is the fully qualified version of FileName including the path. (There is also a SafeFileNames property.)
Multiselect, of type bool. This controls whether the user may select more than one file at a time (true) or not (false). The default is false.

There are more properties; for instance, the Filter property gets or sets a string to limit the types of files involved.

The dialog box may or may not contain a "read-only" checkbox. It will do so if the ShowReadOnly property is set to true. (The default is false.) The ReadOnlyChecked property, a bool, indicated whether the read-only checkbox has been selected (true) or not (false). (The default is false.)

One of the methods is:

     Stream OpenFile()

which opens the file specified by FileName with read-only permission. If we want read/write permission, we will have to open the file by some other method.

There are also SaveFileDialog and PrintFileDialog classes. Both of these and OpenFileDialog are inherited from the FileDialog class.

FontDialog Class

The FontDialog class provides a dialog box enabling the user to select a font including size and effects such as boldface or italics.

The most important property is Font, of type Font, which identifies the user's choice.

Other properties include MaxSize and MinSize, integers, that control the maximum and minimum point sizes allowed.

The ShowColor property, a bool, indicates whether the dialog box includes an option to choose a color. The Color property, of type Color, indicates the user's choice (default = Black).