Delphi Visual Component Library

The VCL is made up of objects, most of which are also components. Using the objects and components of VCL, you are unlimited in the range of Windows programs you can develop rapidly. Delphi itself was built using VCL. Delphi objects contain both code and data. The data is stored in the fields and properties of the objects, and the code is made up of methods that act upon the field and property values. All objects descend from the ancestor object TObject. Components are visual objects that you...

TDBList Box component

The TDBListBox component is a data-aware list box. It allows the user to change the value of the field of the current record in a dataset by selecting an item from a list. The selected item becomes the new value of the field. Link the database list box with a dataset by specifying the data source component (TDataSource) that identifies the dataset as the value of the memo's DataSource property. Specify the field in the dataset you want to access as the value of the DataField property. You...

TList Box componentStd Ctrls

The TListBox component is a Windows list box. A list box displays a list from which users can select one or more items. The list of items in the list box is the value of the Items property. The ItemIndex property indicates which item in the list box is selected. You can add, delete, and insert items in the list box using the Add, Delete, and Insert methods of the Items object, which is of type TStrings. For example, to add a string to a list box, you could write this line of code You can change...

TVar BytesField component

A TVarBytesField represents a field of a record which is represented by a value consisting of an arbitrary set of up to 65535 bytes. The first two bytes are a binary value defining the actual length. Use the Assign method to copy values from another field to a TVarBytesField. The TVarBytesField component has the properties, methods, and events of the TField Delphi Visual Component Library Reference 963 VString PString VPointer Pointer VPChar PChar VObject TObject VClass TClass TVarRec type is...

TGraphic Field component

A TGraphicField represents a field of a record which is represented by a value consisting of an arbitrary set of bytes with indefinite size. The bytes should correspond to graphics data. Use the Assign method to transfer another component to a TGraphicField. Use the LoadFromFile method to load a field's contents from a file. Use LoadFromStream method to load a field from a Stream. Use SaveToFile method to write a field's contents to a file. Use SaveToStream method to write a field's contents to...

TTab Set componentTabs

The TTabSet component presents horizontal tabs users can click to initiate actions. Tab set controls are commonly used with TNotebook controls to display pages within the same dialog box. You create a set of tabs for the tab set control when you specify a list of strings as the value of the Tabs property. One tab is created for each string. If you are using a tab set control to work with a notebook control TNotebook , this line of code creates a tab for each page of the notebook control Then,...

TDBRadio Group componentDBCtris

The TDBRadioGroup component displays a group of data-aware radio buttons. Only one of the radio buttons can be selected at a time, so the radio buttons present a set of mutually exclusive choices. Using a database radio button group box, you can ensure that the user must enter one of the presented options in a field, or the database radio group box can display the value of data in a field when the field is limited to a few possible values. For example, if only the values Red, Green, and Blue...

TCurrency Field component

A TCurrencyField represents a field of a record in a dataset. It is represented as a binary value with a range from positive or negative 5.0 10 to 1.7 10 . It has an accuracy of 15 to 16 digits. Use TCurrencyField for fields that hold currency values. Set the DisplayFormat property to control the formatting of the field for display purposes, and the EditFormat property for editing purposes. Use the Value property to access or change the current field value. The TCurrencyField component has the...

TDDEClient Conv component

A TDDEClientConv component establishes a Dynamic Data Exchange DDE conversation with a DDE server application. Use it in conjunction with a TDDEClientItem component to make your application a DDE client. To link to a DDE server application, define the DDE conversation by specifying the server application name in the DDEService property and the topic of the DDE conversation in the DDETopic property. To establish a link at design time, click the ellipsis button for DDEService or DDETopic in the...

TDrive ComboBox componentFile Ctrl

The TDriveComboBox component is a specialized combo box that displays all the drives available when the application runs. When the user uses the combo box to select another drive, the value of the Drive property changes. You can specify whether the text in the drive combo box is uppercase or lowercase with the TextCase property. If your application uses the drive combo box with a directory list box and a file list box, you can synchronize them with this code written in the drive combo box...

TDBCombo Box componentDBCtrls

A TDBComboBox component is a data-aware combo box control. It allows the user to change the value of the field of the current record in a dataset either by selecting an item PopupMenu ReadOnly ShowHint t gt Showing amp State TabOrder ValueChecked ValueUnchecked Visible Width from a list or by typing in the edit box part of the control. The selected item or entered text becomes the new value of the field if the database combo box's ReadOnly property is False. How a database combo box appears and...

TField component

TField components are used to access fields in a record. By default, a set of TField components is created automatically each time a dataset component is activated the resulting set of TField components is dynamic, mirroring the actual columns in an underlying physical table at that time. At design time, you can use the Fields Editor to create a persistent, unchanging set of TField components for a dataset. Creating TField components with the Fields Editor provides efficient, readable, and...

TDBGrid componentDBGrids

The TDBGrid component can access the data in a database table or query and display it in a grid. Your application can use the data grid to insert, delete, or edit data in the database, or simply to display it. The most convenient way to move through data in a data grid and to insert, delete, and edit data is to use the database navigator TDBNavigator with the data grid. The Fields property is an array of all the fields in the dataset displayed in the data grid. To determine which field is the...