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LISTING 3.3.2 Continued

216:{

217:Application.Run(new datasetapp());

218:}

219:}

220:}

Let’s examine Listing 3.3.2 in more detail. The main initialization of the DataSet takes place on lines 73–88. Here, a DataSet is created and a new table placed in its tables collection. The table is given a set of columns that are identified by the strings “First”, “Name”, and so on.

Adding data to a table is done one row at a time. The method on lines 57–69 adds a new row to the end of the table and optionally fills it with text. You could also create a table with numeric values or other types.

Lines 92–99 do the binding of the data in the table to the Text property of the identified controls. These controls can now be used to edit the information in the table, and they will display each entry automatically as you navigate through the database.

The button handlers that do the navigation are on lines 24–37. These use the ContextManager.Position property to index the rows in the table.

Figure 3.3.2 shows a screenshot of the application.

FIGURE 3.3.2

The DataSet simple binding application.

Complex Binding of Controls to Data

Simple binding is the process of tying a single control to a single data item. Complex binding ties a single control to many data items. Controls that are often used for complex data binding include DataGrid which has the appearance of a simple spreadsheet. This control can display, edit, or add and delete records from a table. A single databinding operation is used to attach the

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control to a DataTable. The DataGrid can only be used to show one table at a time, but it can be used to show relationships between tables.

Listing 3.3.3 shows a modified version of the simple binding example demonstrated in Listing 3.3.2. This listing removes all the controls associated with the DataSet and replaces them with a complex bound grid control. Don’t be put off by the title. Complex data binding is complex only in its function, not its usage.

LISTING 3.3.3 gridbind.cs: An Example of Complex Data Binding

1:namespace Sams

2:{

3:using System;

4:using System.Drawing;

5:using System.Collections;

6:using System.Data;

7:using System.ComponentModel;

8:using System.Windows.Forms;

10://This application shows simple data binding to a

11://programatically created dataset.

12:public class GridBind : System.Windows.Forms.Form

13:{

14:private System.ComponentModel.Container components;

15:private System.Windows.Forms.DataGrid dataGrid1;

17://The dataset used to store the table

18:private DataSet dataset;

19:

20://Called at creation to initialize the

21://dataset and create an empty table

22:private void InitDataSet()

23:{

24:dataset = new DataSet(“ContactData”);

26: DataTable t=new DataTable(“Contacts”); 27:

28:t.Columns.Add(“First”,typeof(System.String));

29:t.Columns.Add(“Name”,typeof(System.String));

30:t.Columns.Add(“Company”,typeof(System.String));

31:t.Columns.Add(“Title”,typeof(System.String));

32:t.Columns.Add(“Phone”,typeof(System.String));

34: t.MinimumCapacity=100; 35:

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36:dataset.Tables.Add(t);

37:}

38:

39://Called at initialization to do complex binding of the DataGrid

40://to the dataset’s “Contacts” table entries

41:private void BindGrid()

42:{

43:this.dataGrid1.SetDataBinding(dataset.Tables[“Contacts”],””);

44:}

45:

46://Constructor. Positions the form controls,

47://Ininitializes the dataset, binds the controls and

48://wires up the handlers.

49:public GridBind()

50:{

51:InitializeComponent();

52:

53: InitDataSet(); 54:

55: BindGrid(); 56:

57: } 58:

59://Cleans up the Form

60:public override void Dispose()

61:{

62:base.Dispose();

63:components.Dispose();

64:}

65:

66://Method added by the form designer

67:private void InitializeComponent()

68:{

69:this.components = new System.ComponentModel.Container ();

70:this.dataGrid1 = new System.Windows.Forms.DataGrid ();

71:dataGrid1.BeginInit ();

72:dataGrid1.Location = new System.Drawing.Point (8, 16);

73:dataGrid1.Size = new System.Drawing.Size (472, 224);

74:dataGrid1.DataMember = “”;

75:dataGrid1.TabIndex = 0;

76:this.Text = “GridBind”;

77:this.AutoScaleBaseSize = new System.Drawing.Size (5, 13);

78:this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;

79:this.ClientSize = new System.Drawing.Size (486, 251);

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LISTING 3.3.3 Continued

80:this.Controls.Add (this.dataGrid1);

81:dataGrid1.EndInit ();

82:}

83:

84:

85:

86://Main method to instantiate and run the application.

87:static void Main()

88:{

89:Application.Run(new GridBind());

90:}

91:}

92:}

Compile this program with the following command line:

csc /t:winexe gridbind.cs

Looking at the information in Listing 3.3.3, you can see that the code used to navigate the data set is no longer needed. The method to add a new row of data is not needed either. The DataGrid control does all that for you. Binding the data to the grid takes place on line 43. Initialization of the data set is identical to the previous example; it is shown on lines 22–37. Figure 3.3.3 shows the GridBind application in action. Notice that the grid provides column and row headers that allow you to select a whole row or order the table according to column alphabetic order.

FIGURE 3.3.3

Complex binding to a DataGrid.

The DataGrid control can also be used to show hierarchical relationships between multiple data tables. Perhaps a Customer Resource Management application would want to show the relationship between a customer and his or her orders or a client and his or her technical support incidents. Complex binding of data makes this otherwise difficult process painless.