Requirements for this Issue

The source code in this issue is designed for Visual Basic 4 and up. It also requires a copy of True DBGrid from APEX Software Corporation. We use this grid in all our applications that need a data grid. Based on your subscription responses many of you already use True DBGrid.

In this Issue

This issue shows how to easily use the ValueItem feature of True DBGrid. Apex explains the ValueItem feature as such:

• A ValueItem object defines an allowable input value for a Column object, and may also define a mapping between the underlying data value and its display representation, either textual or graphical. Each grid column stores these items, if specified, in a ValueItems collection, which is accessed using the ValueItems property.

You can get more details on the ValueItems feature by reviewing the help file for True DBGrid. It should be called TDBGRID.HLP and is usually located in your Windows or Windows System directory. You should also be able to access it by clicking a True DBGrid object in the Visual Basic design environment and pressing the F1 key. This usually brings up context sensitive help in Visual Basic.

LoadColumnCombo

Public Sub LoadColumnCombo(DBGrid As TDBGrid, sDBName As String, _
                  sSQL As String, sColumn As String, sDisplayField As String, _
                  sValueField As String)

Parameters

• DBGrid - The True DBGrid to update
• sDBName - The name of the database to get the data from to load into the ValueItems collection.
• sSQL - The query to get the data from the database named sDBName.
• sColumn - The name of the column to update in the True DBGrid.
• sDisplayField - The field of data to load into the ValueItems collection that will be displayed in the combo box.
• sValueField - The field of data to load into the ValueItems collection that will be stored in the data field the column is referencing. For example, if the column in the DBGrid is referencing the field called [Payment Type], sDisplayField will be displayed on the screen and sValueField will be stored in the field in the database.

Return Value

None unless an error occurs. If an error occurs this routine will raise the error to the calling subroutine.

Sample Usage

We will demonstrate an example of this routine. The most likely place this routine will be used is in startup code for a form that contains a True DBGrid on it.

The below example assumes the following:

• grdData is the name of the True DBGrid
• sDBName is the name of the database (example: "C:\DATA\DATA.MDB")
• "SELECT * FROM [Payment Methods]" is the query to retrieve all the records from the [Payment Methods] table in the database sDBName
• "Payment Type" is the name of the column that this routine should add a ValueItems collection to.
• "Description" is the text from the [Payment Methods] table that you want the user to view. In this example choices would probably be items like Visa, MasterCard, Check, Cash, American Express
• "ID" is the primary index value from the [Payment Methods] table. Typically in a database application you would not store "Cash" or "Visa" in the actual order records. Instead you would store an index value or an ID value. This value is the value that will be stored in the field specified in column "Payment Type"

Source Code

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Comments on the Source Code

A useful enhancement to this routine would be to define additional parameters to set the Translate, CycleOnClick, Validate and Presentation properties.

This document is available on the web

Summary

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