在 ASP.NET 中生成条形图

• 下载源代码文件 - 1.88 Kb

引言

以下示例演示了如何为网页上可用的任何业务信息生成条形图。它使用 .NET System.Drawing 命名空间中提供的类来生成图表。

下面示例中创建的条形图说明了公司从一月到十二月每个月的利润。

生成条形图

要在 X 轴和 Y 轴上显示的数据存储在 ArrayList 中，然后从这些 ArrayList 中读取数据以创建所需的条形图。

首先，ArrayList 填充如下

Dim aMonths As ArrayList = New ArrayList()
aProfits As ArrayList = New ArrayList()
aMonths.Add("January")
aMonths.Add("February")
aMonths.Add("March")
aMonths.Add("April")
aMonths.Add("May")
aMonths.Add("June")
aMonths.Add("July")
aMonths.Add("August")
aMonths.Add("September")
aMonths.Add("October")
aMonths.Add("November")
aMonths.Add("December")

aProfits.Add(240500)
aProfits.Add(220950)
aProfits.Add(283500)
aProfits.Add(340000)
aProfits.Add(325750)
aProfits.Add(123456)
aProfits.Add(235621)
aProfits.Add(345235)
aProfits.Add(290451)
aProfits.Add(152345)
aProfits.Add(653456)
aProfits.Add(785620)

数据填充完毕后，可以通过调用方法 DrawBarGraph 生成图表

DrawBarGraph("Profits!", aMonths, aProfits)

DrawBarGraph 定义如下

Sub DrawBarGraph(ByVal strTitle As String, _
        ByVal aX As ArrayList, ByVal aY As ArrayList)
    Const iColWidth As Integer = 60, iColSpace As Integer = 25, _
          iMaxHeight As Integer = 400, iHeightSpace As Integer = 25, _
          iXLegendSpace As Integer = 30, iTitleSpace As Integer = 50
    Dim iMaxWidth As Integer = (iColWidth + iColSpace) * aX.Count + iColSpace, _
          iMaxColHeight As Integer = 0, _
          iTotalHeight As Integer = iMaxHeight + iXLegendSpace + iTitleSpace

    Dim objBitmap As Bitmap = New Bitmap(iMaxWidth, iTotalHeight)
    Dim objGraphics As Graphics = Graphics.FromImage(objBitmap)
 
    objGraphics.FillRectangle(New SolidBrush(Color.White), _
                0, 0, iMaxWidth, iTotalHeight)
    objGraphics.FillRectangle(New SolidBrush(Color.Ivory), _
                0, 0, iMaxWidth, iMaxHeight)

    ' find the maximum value
    Dim iValue As Integer
    For Each iValue In aY
        If iValue > iMaxColHeight Then iMaxColHeight = iValue
    Next

    Dim iBarX As Integer = iColSpace, iCurrentHeight As Integer
    Dim objBrush As SolidBrush = New SolidBrush(Color.FromArgb(70, 20, 20))
    Dim fontLegend As Font = New Font("Arial", 11), _
        fontValues As Font = New Font("Arial", 8), _
        fontTitle As Font = New Font("Arial", 24)

     ' loop through and draw each bar
    Dim iLoop As Integer
    For iLoop = 0 To aX.Count - 1
        iCurrentHeight = ((Convert.ToDouble(aY(iLoop)) / _
               Convert.ToDouble(iMaxColHeight)) * _
               Convert.ToDouble(iMaxHeight - iHeightSpace))
        objGraphics.FillRectangle(objBrush, iBarX, _
        iMaxHeight - iCurrentHeight, iColWidth, iCurrentHeight)
        objGraphics.DrawString(aX(iLoop), fontLegend, _
           objBrush, iBarX, iMaxHeight)
        objGraphics.DrawString(Format(aY(iLoop), "#,###"), _
           fontValues, objBrush, iBarX, iMaxHeight - iCurrentHeight - 15)
        iBarX += (iColSpace + iColWidth)
    Next
    objGraphics.DrawString(strTitle, fontTitle, objBrush, _
          (iMaxWidth / 2) - strTitle.Length * 6, iMaxHeight + iXLegendSpace)
    'objBitmap.Save("C:\inetpub\wwwroot\graph.gif", ImageFormat.GIF) 

    objBitmap.Save(Response.OutputStream, ImageFormat.Gif)
    objGraphics.Dispose()
    objBitmap.Dispose()
End Sub

这段代码将生成条形图并在屏幕上显示。此外，如果需要，可以将条形图保存为图像，只需取消注释上述代码中的下一行即可

objBitmap.Save("C:\inetpub\wwwroot\graph.gif", ImageFormat.GIF)