MSFlexGrid Tips and Tricks Frank Sommer Microsoft Regional Director, Northern California October 1997 From Regional Director Magazine
Introduction Microsoft« Visual Basic« version 5.0 comes with not one, not two, but three grid controls in the box. The three grids are Grid, DBGrid, and MSFlexGrid. While I'm tempted to say it took them three tries to get it right, the truth is that there are good reasons for the inclusion of all three. After briefly exploring these reasons, and when to use each grid, this article will take an in-depth look at the newest of the three: MSFlexGrid.
Grid is the original Visual Basic grid. It was shipped with the Professional Toolkit for Visual Basic 1.0 back in 1991. DBGrid is a version of the Apex TrueGrid control, and was first shipped with Visual Basic 4.0 in 1995. The newest of the three is MSFlexGrid, a version of the VideoSoft VSFLEX control, and was shipped with Visual Basic 5.0.
In the two-grid world of Grid and DBGrid, Grid was favored for its simplicity, and at one-sixth the size of DBGrid, its small footprint. While you will occasionally find a fan of this minimalist grid, for the most part Grid has been ignored by programmers. Its presence in today's toolbox is largely justifiable only for backwards compatibility. When MSFlexGrid is added to the mix, even this reason goes away, as MSFlexGrid supports nearly all of the properties, methods and events of Grid. At only twice the size, its greatly enhanced feature set makes an excellent replacement for the Grid control in existing projects.
The real question as to which grid to use boils down to a choice between DBGrid and MSFlexGrid. Both grids are full-featured and highly customizable. There are a few obvious points of departure. If you need full data binding choose DBGrid, as the binding in MSFlexGrid is read-only binding. On the other hand, if you need cell merging or data pivoting, MSFlexGrid is your only choice. Beyond that, each grid has its own look and feel, though MSFlexGrid has a clear advantage in its smaller size. MSFlexGrid is very flexible (hence its name) in the ways you can use it. What follows is a discussion, with some code examples, of various techniques you can use with MSFlexGrid.
Getting Data into the Grid There are numerous ways to get data into the MSFlexGrid. There is no "officially" preferred method or clear speed differences, so the proper one to use depends on the source of the data and personal taste. For data contained in a database, the obvious choice is to simply bind the grid to a Data control. Once you set the DatabaseName and RecordSource properties of the Data control, simply use the DataSource property of the MSFlexGrid to bind the grid to the Data control. The grid will populate automatically with data, one row for each record in the database. The first row will contain column headings derived from the field names in the database. If you don't want the automatically created header row, use the RemoveItem method to delete it. Since MSFlexGrid won't allow you to remove a header (fixed) row, you will have to first set the FixedRows property to zero.
In its unbound mode, MSFlexGrid is a data container: you put the data in once, and it remains there for the life of the application. There are four properties and one method to help you do this: the AddItem method, and the Clip, Text, TextArray, and TextMatrix properties.
If you are using the grid as a listbox, or prefer to think of it as a listbox, use the AddItem method to populate it. The following code will create a two-column grid with the letters A through Z, and their ASCII codes.
MSFlexGrid1.Rows = 0 For I = Asc("A") To Asc("Z") MyData = Chr$(I) & vbTab & I MSFlexGrid1.AddItem MyData Next
The AddItem method will add 26 rows to those already in the grid. We set the rows property to zero before starting so that the finished grid will have only 26 rows total. Note how the embedded tab character (vbTab) is used to separate the data for the second column. The AddItem method also has an optional index parameter that allows you to add the row at a specific location.
The Clip property is useful to quickly populate a grid with a range of data from any data source that has a compatible Clip method. An rdoResultset is just such a source, and the GetClipString method does the trick. The code sample below will take the first four rows of the Customers table and copy them into rows five through eight of a grid:
Dim rs As rdoResultset Set rs = MyConnection.OpenResultset("Customers") 'select the target range MSFlexGrid1.Row = 5 MSFlexGrid1.Col = 1 MSFlexGrid1.RowSel = 8 MSFlexGrid1.ColSel = rs.rdoColumns.Count 'get the data MSFlexGrid1.Clip = rs.GetClipString(4) 'returns 4 rows
Notice that we did not have to deal with the data at the Field level, the Clip property did all of that for us. The Clip property returns data as well as setting it, so you can use it to cut and paste from one area of a grid to another.
The Text property is frequently used to set the contents of a single cell. That cell however must be the current cell, so you must first use the Row and Col properties to select the desired cell. To set a range of cells to the same value, use the FillStyle property in conjunction with the Text property. The code below puts an "X" in each cell of a grid:
If you don't want the current cell to change when you load data as it does with the Text property, you should use the TextArray or TextMatrix property. These properties set the contents of an arbitrary cell without changing the Row or Col properties. TextMatrix addresses a cell using the familiar row and column notation. TextArray uses an index to identify a cell. The index is simply a zero-based enumeration of the cells from left to right, top to bottom. In a 2 x 2 grid the following lines both address the lower right-hand cell:
MSFlexGrid1.TextArray(3) = "X" MSFlexGrid1.TextMatrix(1,1) = "X"
As you can see, there is a great variety of ways to place data into the MSFlexGrid. Use the one that makes the most sense to you for the occasion.
Sorting Techniques MSFlexGrid has a built-in sorting capability that is fairly flexible, and also very fast. In most cases it is faster to use the built-in sorting than it is to use an ORDER BY clause in your SQL statement. The sorting options allow you to sort ascending or descending with a numeric sort or a string sort. The string sort can be set to ignore case, if desired. The Sort property specifies which type of sort should be done. The Sort property can also be thought of as a method because the sorting action occurs as soon as the property is set. You can sort on multiple columns to give the effect of a multikey sort.
There are two techniques that can be used for more sorting flexibility. Setting the Sort property to flexSortCustom causes a special event, Custom, to fire whenever the grid is sorted. You can use this event to implement any type of sort you wish. The second method uses a hidden column and lets the grid do the work. Suppose you have a database field that returns a date in the Short Date format. Neither a numeric sort nor a string sort would order this column correctly. To sort by date you need to add an extra column to the grid and set its width to zero. Populate the column with values obtained by converting the date to a number, and sort on that column as demonstrated below (assumes the date field is in column 2):
Dim Ro As Integer Dim SortCol As Integer Dim SortDate As Double
'add a column to hold the sort key MSFlexGrid1.Cols = MSFlexGrid1.Cols + 1 SortCol = MSFlexGrid1.Cols - 1 MSFlexGrid1.ColWidth(SortCol) = 0 'invisible 'calculate key values & populate grid For Ro = 1 To MSFlexGrid1.Rows - 1 SortDate = DateValue(MSFlexGrid1.TextMatrix(Ro, 2)) MSFlexGrid1.TextMatrix(Ro, SortCol) = SortDate Next Ro 'do the sort MSFlexGrid1.Col = SortCol 'set the key MSFlexGrid1.Sort = flexSortNumericAscending
Editing Grid Data MSFlexGrid does not have a built-in cell editing capability, but it provides the hooks to make it easy for you to add that capability programmatically. The advantage of this approach is that you can tailor editing behavior to your taste. The basic technique involves smoke and mirrors: the editing occurs not in MSFlexGrid at all, but in a standard Textbox control that is positioned precisely over the cell being edited. In this example, we will give the user two ways to get into the edit mode, either by double-clicking on a cell, or by simply starting to type in the current cell. The following two routines implement this: Private Sub MSFlexGrid1_DblClick() GridEdit Asc(" ") End Sub
Private Sub MSFlexGrid1_KeyPress(KeyAscii As Integer) GridEdit KeyAscii End Sub In each case we call a grid edit subroutine and pass it a keystroke. In the case of double-clicking, we pass the space character as a flag. The GridEdit routine initializes the edit box and moves it into position: Sub GridEdit(KeyAscii As Integer) 'use correct font Text1.FontName = MSFlexGrid1.FontName Text1.FontSize = MSFlexGrid1.FontSize Select Case KeyAscii Case 0 To Asc(" ") Text1 = MSFlexGrid1 Text1.SelStart = 1000 Case Else Text1 = Chr(KeyAscii) Text1.SelStart = 1 End Select
'position the edit box Text1.Left = MSFlexGrid1.CellLeft + MSFlexGrid1.Left Text1.Top = MSFlexGrid1.CellTop + MSFlexGrid1.Top Text1.Width = MSFlexGrid1.CellWidth Text1.Height = MSFlexGrid1.CellHeight Text1.Visible = True Text1.SetFocus End Sub For demonstration purposes, the Case statement in the GridEdit routine shows two different behaviors when entering the edit mode. In practice you would probably only use one of them, or a different one of your own creation. If the edit mode is entered by virtue of a double-click or a control key press, we copy the contents of the grid cell to the exit box and place the cursor at the end of the string. If the edit mode is entered by pressing a normal key, we ignore the original cell contents and insert the pressed key into the edit box. The positioning of the exit box could be done on one line with the Move method. Here we have used four lines so that it reads more easily in this article. Notice that MSFlexGrid conveniently gives us all the coordinate information we need. Next, we need a couple of routines that handle housekeeping when the user moves to a different cell or moves focus back to the grid from another control. The LeaveCell event is also the place where you would put any data validation code that might be applicable. Private Sub MSFlexGrid1_LeaveCell() If Text1.Visible Then MSFlexGrid1 = Text1 Text1.Visible = False End If End Sub
Private Sub MSFlexGrid1_GotFocus() If Text1.Visible Then MSFlexGrid1 = Text1 Text1.Visible = False End If End Sub Next we place some navigation code in the KeyDown event of the edit box so that, for instance, the user can leave the edit mode by pressing ESC, and move to a different row by pressing an arrow key: Private Sub Text1_KeyDown(KeyCode As Integer, Shift As Integer) Select Case KeyCode Case vbKeyEscape Text1.Visible = False MSFlexGrid1.SetFocus Case vbKeyReturn MSFlexGrid1.SetFocus Case vbKeyDown MSFlexGrid1.SetFocus DoEvents If MSFlexGrid1.Row < MSFlexGrid1.Rows - 1 Then MSFlexGrid1.Row = MSFlexGrid1.Row + 1 End If Case vbKeyUp MSFlexGrid1.SetFocus DoEvents If MSFlexGrid1.Row > MSFlexGrid1.FixedRows Then MSFlexGrid1.Row = MSFlexGrid1.Row - 1 End If End Select End Sub Finally we need a line of code to suppress the Beep that occurs when ENTER is pressed in a Textbox: Private Sub Text1_KeyPress(KeyAscii As Integer) 'noise suppression If KeyAscii = vbKeyReturn Then KeyAscii = 0 End Sub In order for the edit box to merge seamlessly into the grid, you need to set several Textbox properties at design-time: set Appearance = 0 (flat), and BorderStyle = 0 (none). Also set Visible = False so that the edit box is not initially visible. To really fine-tune this code, the edit box needs a slight additional offset to the southeast (with a corresponding reduction in size) so that the text in it lines up exactly with the text in the cell beneath. You would probably also want to write some code behind the scroll event of the grid since clicking on the grid's scroll bar will not cause the edit box to loose focus. Note that this technique is not limited to using a Textbox as your edit box. You could modify the sample code to use a ComboBox, a CheckBox, or even a calendar control for editing, based on the column being edited. MSFlexGrid is a very flexible control indeed, and this article just touches on some of the things you can do with it. As you gain familiarity with it, it will become a more regular part of your toolbox. Cell merging and pivoting are two more unique features of the MSFlexGrid that give it tremendous power and bear investigation.