TcxGridDBColumn Class

A column in a data-aware grid Table View.

Declaration

TcxGridDBColumn = class(
    TcxGridColumn
)

Remarks

A column in a data-aware Table View is designed to display values from a dataset field. Use the DataBinding property to bind a data-aware column to data.

In-Place Editors

A column can use any unbound editor shipped with the ExpressEditors Library as an in-place editor for cell edit operations. An in-place editor instance exists (and, therefore, consumes memory and other system resources, such as a WinAPI handle) only when a column cell is being edited. Otherwise, the column displays a static editor image for resource usage optimization.

To switch between available editors, you can use the PropertiesClassName or PropertiesClass property. Use the Properties property to configure the in-place editor associated with the column.

Default In-Place Editor and Data Types

When PropertiesClassName and PropertiesClass properties are unspecified, the data type of the underlying dataset field determines the active in-place editor according to the following table:

Dataset Field Type	Default In-Place Editor	Description
ftBoolean	TcxCheckBox	A check box editor with support for three states.
ftCurrency, ftBCD, and ftFMTBcd	TcxCurrencyEdit	A numeric editor for currency values.
ftDate and ftDateTime	TcxDateEdit	A date editor with a drop-down calendar.
ftTime	TcxTimeEdit	A spin editor for time values.
ftBytes, ftVarBytes, ftBlob, ftFmtMemo, ftParadoxOle, ftDBaseOle, and ftTypedBinary	TcxBlobEdit	A Binary Large Object (BLOB) editor.
ftMemo	TcxMemo	A multi-line editor for plain text.
ftGraphic	TcxImage	An editor designed to display images.
All other types	TcxMaskEdit	A single-line text editor with support for input masks.

Main API Members

The list below outlines key members of the TcxGridDBColumn class. These members allow you to configure columns in data-aware Table grid Views.

General Appearance Settings

ApplyBestFit | BestFitMaxWidth

Allow you to adjust the column width to display content in full and limit the maximum column width in this mode.

Caption | AlternateCaption

Specify main and alternative captions for the column. An alternative column caption can replace the main caption in customization dialogs, filter panels, etc.

HeaderGlyph | HeaderImageIndex

Allow you to assign a glyph to the column header.

OnCustomDrawCell

Allows you to override or complement column draw routines.

OnGetDisplayText | OnGetFilterDisplayText

Allow you to customize display text and column captions displayed in a filter drop-down window.

OnGetFilterImages | OnGetFilterValues

Allow you to customize the column’s filter drop-down window.

Styles

Allows you to customize the appearance of different column elements.

Column Layout Settings

FooterAlignmentHorz

Allows you to position column footer cells.

HeaderAlignmentHorz | HeaderAlignmentVert

Position the column header horizontally and vertically.

HeaderGlyphAlignmentHorz | HeaderGlyphAlignmentVert

Specify the glyph position within the column header.

LayoutItem | RowLayoutItem

Allow you to configure the column in a custom row layout.

MinWidth

Specifies the minimum column width, in pixels.

In-Place Editor Settings

Editing

Specifies if the assigned in-place cell editor is active.

OnGetProperties

Allows you to display different in-place editors for different records or customize editor settings based on custom conditions.

OnGetPropertiesForEdit

Allows you to change the assigned in-place editor and customize its settings when a user invokes the editor.

Properties

Provides access to the settings of the assigned in-place editor.

PropertiesClass

Specifies the active in-place editor class. At design time, you can use the Properties node in the Object Inspector to assign an in-place editor to the column and configure the editor.

RepositoryItem

Allows you to associate the column with a repository item that defines the required in-place editor and its settings.

Tip

Repository items are particularly useful if you need to share in-place editor settings between multiple grid View items or customize editor settings in OnGetProperties and OnGetPropertiesForEdit event handlers.

Data Management

DataBinding

Provides access to data binding settings.

GroupIndex

Allows you to group columns in the parent grid View by the current column.

SortIndex | SortOrder

Allow you to sort data in the parent grid View against the current column.

Grid View-Related API Members

IsBottom | IsLeft | IsMostBottom | IsMostLeft | IsMostRight | IsRight | IsTop

Allow you to identify the column’s position within the parent grid View.

FixedKind

Allows you to fix the column or dock it to the left when users scroll the parent grid View to the right.

Focused

Specifies if the column has focus.

Index

Defines the column position in its parent grid View.

IsFirst | IsLast

Identify if the column is the first or last in the parent grid View’s collection of visible columns.

IsPreview

Allows you to identify if the column has a preview section.

MakeVisible

Scrolls the parent grid View to display the current column.

Selected

Identifies if the column is selected.

Summary

Provides access to column summary settings.

VisibleForEditForm | VisibleForRowLayout

Specify if the column is visible in an in-place Edit Form and the custom row layout.

General-Purpose API Members

Editable

Allows you to identify if the column is editable.

GridView

Provides access to the parent grid View.

Options

Allows you to configure general column settings.

RestoreDefaults

Restores the default values of column type-specific settings, such as Caption and Width.

ShowExpressionEditor

Invokes the Expression Editor dialog.

Visible

Specifies if the column is visible.

Code Example: Create a Data-Aware Column

The following code example creates a data-aware column, associates it with a field in the dataset bound to the parent grid Table View, sorts data against the created column in descending order, sets a single-line text editor as the column’s in-place editor, and customizes editor settings:

Delphi

uses cxTextEdit;
// ...
var
  AColumn: TcxGridDBColumn;
  ATextEditProperties: TcxTextEditProperties;
begin
  AColumn := cxGrid1DBTableView1.CreateColumn;  // Creates a new data-aware column
  AColumn.DataBinding.FieldName := 'ContactName'; // Binds the created column to the "ContactName" field
  cxGrid1DBTableView1.DataController.ClearSorting(False);  // Clears the current sorting
  AColumn.SortOrder := soDescending;  // Sorts data against the created column in descending order
  AColumn.PropertiesClass := TcxTextEditProperties; // Assigns an in-place single-line text editor
  ATextEditProperties := AColumn.Properties as TcxTextEditProperties;
  ATextEditProperties.BeginUpdate;  // Initiates the following batch change
  try
    ATextEditProperties.Nullstring := 'Add a contact name'; // Prompts users to enter a contact name
    ATextEditProperties.UseNullString := True;  // Displays the defined text hint in an empty editor
    ATextEditProperties.MaxLength := 30;  // Limits the maximum contact name length
    ATextEditProperties.Alignment.Horz := taCenter;  // Centers column content
  finally
    ATextEditProperties.EndUpdate;  // Calls EndUpdate regardless of the batch operation's success
  end;
end;

C++

#include "cxTextEdit.hpp"
// ...
  TcxGridDBColumn *AColumn;
  TcxTextEditProperties *ATextEditProperties;
  // ...
  AColumn = cxGrid1DBTableView1->CreateColumn();  // Creates a new data-aware column
  AColumn->DataBinding->FieldName = "ContactName"; // Binds the created column to the "ContactName" field
  cxGrid1DBTableView1->DataController->ClearSorting(false);  // Clears the current sorting
  AColumn->SortOrder = soDescending;  // Sorts data against the created column in descending order
  AColumn->PropertiesClass = __classid(TcxTextEditProperties); // Assigns an in-place single-line text editor
  ATextEditProperties = dynamic_cast<TcxTextEditProperties*>(AColumn->Properties);
  ATextEditProperties->BeginUpdate();
  try
  {
    ATextEditProperties->Nullstring = "Add a contact name"; // Prompts users to enter a contact name
    ATextEditProperties->UseNullString = true;  // Disables the defined hint text in an empty editor
    ATextEditProperties->MaxLength = 30;  // Limits the maximum contact name length
    ATextEditProperties->Alignment->Horz = taCenter;  // Centers column content
  }
  __finally
  {
    ATextEditProperties->EndUpdate();  // Calls EndUpdate regardless of the batch operation's success
  }

Grid Column Deletion

To delete a grid column, release it directly in code (call the Free procedure in Delphi or use the delete keyword in C++Builder):

Delphi

  cxGrid1DBTableView1Column1.Free;

C++

  delete cxGrid1DBTableView1Column1;

Direct TcxGridDBColumn Class References

The following public API members reference a TcxGridDBColumn object:

TcxGridDBTableView.Columns

Provides indexed access to the collection of the View’s columns.

TcxGridDBTableView.CreateColumn

Creates a column and adds it to the Columns collection.

TcxGridDBTableView.GetColumnByFieldName

Locates the column displaying a particular field’s values.

Other Grid Column Classes

Unbound

TcxGridBandedColumn

A column in an unbound Banded Table View.

TcxGridColumn

A column in an unbound grid Table View.

Data-Aware

TcxGridDBBandedColumn

A column in a data-aware Banded Table grid View.

Server Mode

TcxGridServerModeColumn

A column in a Server Mode grid Table View.

TcxGridServerModeBandedColumn

A column of a Banded Table View in Server Mode.

Related Compiled Demo

To see the Table grid View in action, run the Grid and Data Editors demo in the VCL Demo Center installed with compiled DevExpress demos. Click the Fixed Columns item in the side bar to the left.

Download: Compiled VCL Demos

Tip

You can find full source code for installed compiled Data Grid demos in the following folder:

%PUBLIC%\Public Documents\DevExpress VCL Demos\MegaDemos\Product Demos\ExpressQuantumGrid

Inheritance

TObject

TPersistent

TComponent

TcxCustomComponent

TcxComponent

TcxCustomGridTableItem

TcxCustomGridColumn

TcxGridColumn

TcxGridDBColumn