DateTime, Code Regions, and Multiple Form Applications

Part13dbg

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DateTime

• DateTime is used for storing and converting time and date values.

• The Now property of the DateTime object delivers the present time and date from the system clock.DateTime currentDateTime = DateTime.Now;

• The Today property of DateTime object is the date portion only.DateTime currentDate = DateTime.Today;

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Working With DateTime

• Declare a DateTime object:DateTime myDT = new DateTime();

• Get present time and date:myDT = DateTime.Now;

• Extract time or date value:lblDay.Text =

myDT.DayOfWeek.ToString();• DayOfWeek, DayofYear, Day, Hour, Second,

Month, Year properties allow access to various parts of DateTime.

DateTimeStruct

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Formatting DateTime output

• Use Format Specifiers with ToString()

• or use ToLongDateString(), ToLongTimeString(), ToShortDateString(), or ToShortTimeString() methods.

dDtTfF

6/4/2007Monday, June 04, 200712:00 AM12:00:00 AMMonday, June 04, 2007 12:00 AMMonday, June 04, 2007 12:00:00 AM

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Generate DateTime Values with DateTimePicker Control• The DateTimePicker control furnishes a visible

interface for selecting DateTime values.• Dates are selected with a perpetual calendar

display.• Times and dates may be displayed in several

formats.• Use the TimeSpan class to manipulate and

compare times and dates.

DatePicker

Code Regions

Showing/Hiding and Creating Code Regions

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Regions in Code

• We have seen before that the region, Windows Form Designer Generated Code, is a collapsible region.

• When we want to view the contents, we click the in front of region.

• To collapse the region, we click the in front of region.

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Making Your Own Collapsible Regions in Code• You can make your own collapsible region in

code, for example, a region for the class-level variables.

• Type #region regionDescription above the class-level variable declarations.

• Type #endregion after the last line of class-level variable declarations.

• You will now have a user-defined region.

Multiple Form Applications

Single Document Interface

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Launching a Second Form• Use the Add Windows Form…

selection from the Project menu.

• A new form class is added to the project.

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Launching a Second Form

• An instance of the second form must be created within the original application form.

• Once the form object is created, it may be displayed by running its Show() method.

• Multiple instances of the second form can be created and displayed.

SecondSDI

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Startup Form as “Parent”

• Launching a second form in this way causes the second form to depend upon the first for survival.

• Closing the first form causes the second form to close as well.

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Hiding a Form

• Run the Hide() method of the original form to remove it from view prior to showing the second form.

• Now the second form commands the application and can not lose focus unless it is closed.

• Closing the second form leaves the original form running, but not visible.

HideParent

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Showing a Hidden Form

• We could run the Show() method of the original form from the second form—but only if the second form is aware of the first form

• If we created a new instance of the first form within the second form it would be different from the original.

• One way to solve the problem is to pass the identity of the original form to the second form as a constructor argument.

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Identifying the Parent Form

• If the second form has a class scope variable of type Form, the constructor can use its argument to assign the identity of the “parent” form.

• This then allows the second form to run the Show() method of the “parent”.

FormConstructor

Multiple Form Applications

Owned Forms

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Owned Forms

• Subsequent SDI forms can be launched from a startup form as Owned Forms.

• Although these forms can transfer focus back to the startup form they remain on top of the startup form at all times.

• Add a new form to the Owned Forms collection of the startup form by setting its Owner property to the startup form.

OwnedForms

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Owned Forms

• Potential uses for owned forms are as specialized help forms, customized “toolboxes” or overview maps.

• Use an owned form when you don’t want to lose sight of a form in a multiple SDI application, even if it loses focus.

Multiple Form Applications

Multiple Document Interface

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MDI Forms

• Standard Windows forms may exist as either MDI parents or MDI children.

• MDI children may only be displayed within the client area of their parent and may not be dragged outside that client area.

• Like owned forms, MDI children always remain on top of their parent form.

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MDI Parent Forms

• Any standard Windows form can be converted to an MDI parent by setting its IsMdiContainer property to True.

• By convention, MDI parent forms have a dark gray client area.

• Because MDI parents are intended solely as containers for other forms, they should not include controls.

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MDI Parent Forms

• Use menu items in the MenuStrip control of the MDI parent to control activities associated with displaying MDI child forms.

MDIParent

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MDI Child Forms

• Forms destined to become children of an MDI parent should be instantiated within the MDI parent class.

• Any standard Windows form can become an MDI child.

• Set the MdiParent property of the child instance to the parent.

• Show the child form.

MDIChildren

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MDI Child Form Menus

• When an MDI Child has focus within an MDI parent form, the menustrips of the Parent and Child are merged and menuitems from both are displayed.

• The merging of the menus to present a sensible display is coordinated by adjusting the MergeAction and MergeIndex properties of each menuitem.

• The Visible property of the child menustrip must be set to false if you do not wish to see both parent and child menustrips.

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The Windows Menu

• By design convention the Menustrip of an MDI parent form has a Window menu item that lists the displayed child forms and indicates which has focus.

• The contents of this menuitem (mnuWindow) are automatically generated by simply setting the MdiWindowListItem property of the parent menustrip to the appropriate menuitem (mnuWindow).

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The Window Menu

• Three different modes of display are available for child forms: cascade, horizontal tile, and vertical tile.

• These modes can be set with the LayoutMdi() method of the parent form.

• Use the foreach loop to close all forms in the child collection of the parent at once.

MDIWindows