之前我们曾经提到过,您可以在Windows Form窗体上的一个DataGridView控件中一次显示出多个圆饼图(或其它形式的统计图表)以便能够一次检视多个群组数据的比例情况(如图表1所示)。当时并未列出原始程序代码,有读者希望能够提供原始程序代码,所以我们在此将其完整列出,与大家共享:(注:本程序范例将附于简体版的「Visual C# 2005文件IO与资料存取秘诀」一书)
Option Strict On
Imports System.Data.SqlClient
Imports System.Drawing
Imports System.IO
Imports System.Drawing.Imaging
Public Class Form1
' 宣告各个私用变量。
Private dirInfo As DirectoryInfo
' 此变量用来持有男女平均薪资的总和。
Private TotalSalary As Long
' 此变量用来持有女性平均薪资。
Private FemaleSalary As Long
' 此变量用来持有男性平均薪资。
Private MaleSalary As Long
' 此变量用来持有女性空间之扇形区域之第二个边的角度。
Private sweep As Single
Private Sub Form1_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
Dim myPieChartTable As New DataTable
myPieChartTable.Columns.Add("部门", GetType(System.String))
myPieChartTable.Columns.Add("图形", GetType(System.Byte()))
' 利用 SqlConnectionStringBuilder 对象来构建连接字符串。
Dim connectStringBuilder As New SqlConnectionStringBuilder()
connectStringBuilder.DataSource = "(local)\SQLEXPRESS"
connectStringBuilder.InitialCatalog = "北风贸易"
connectStringBuilder.IntegratedSecurity = True
Using cn1 As New SqlConnection(connectStringBuilder.ConnectionString)
Dim cmdDepartment As New SqlCommand( _
"SELECT DISTINCT 部门FROM 章立民研究室", cn1)
cn1.Open()
Using dr1 As SqlDataReader = cmdDepartment.ExecuteReader
While dr1.Read
' 取得部门。
Dim strDepartment As String = dr1.GetSqlString(0).Value
Dim myTable As New DataTable
Using cn2 As New SqlConnection(connectStringBuilder.ConnectionString)
Dim cmdLiming As New SqlCommand( _
"SELECT 性别, AVG(目前薪资) AS 平均薪资 FROM 章立民研究室 " & _
"WHERE 部门= @department GROUP BY 性别ORDER BY 性别", cn2)
cmdLiming.Parameters.Add( _
"@department", SqlDbType.NVarChar, 10).Value = strDepartment
cn2.Open()
Using dr2 As SqlDataReader = cmdLiming.ExecuteReader()
myTable.Load(dr2, LoadOption.OverwriteChanges)
End Using
' 将男女平均薪资的总和指派给变数 TotalSalary。
TotalSalary = CInt(myTable.Rows(0)(1)) + CInt(myTable.Rows(1)(1))
' 将女性平均薪资指派给变量 FemaleSalary。
FemaleSalary = CInt(myTable.Rows(0)(1))
' 将男性平均薪资指派给变量 MaleSalary。
MaleSalary = CInt(myTable.Rows(1)(1))
' 计算女性空间之扇形区域之第二个边的角度。
sweep = CSng(
End Using
Using objBitmap As New Bitmap(300, 330)
Using objGraphics As Graphics = Graphics.FromImage(objBitmap)
objGraphics.Clear(Drawing.Color.White)
' 宣告 Rectangle 结构变量,并指定X 坐标参数、Y 坐标参数、
' 宽度参数、高度参数,用来显示圆饼图的矩形大小。
Dim rect As Rectangle = New Rectangle(40, 10, 200, 200)
' 宣告 Rectangle 结构变量,并指定 X 坐标参数、Y 坐标参数、
' 宽度参数、高度参数,用来当作圆饼图边界的矩形大小。
Dim rect2 As Rectangle = New Rectangle(0, 0, 290, 320)
' 宣告 Rectangle 结构变量,并指定 X