Generating Bar Chart in ASP.NET

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Introduction

The following example demonstrates how to generate bar-charts for any business information available on a web page. This uses the classes which are provided in the .NET System.Drawing namespace to generate the chart.

Bar chart created in the below example illustrates the profit of a company for each month from January through December.

Generating the Bar chart

Data which is to be displayed on X axis and Y axis is stored in ArrayLists, and then the data is read from these ArrayLists for creating the required bar chart.

First, the ArrayLists are populated as follows:

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)

Once the data is populated, the chart can be generated by calling the method DrawBarGraph:

DrawBarGraph("Profits!", aMonths, aProfits)

DrawBarGraph is defined as follows:

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

This code will generate the bar chart and display it on the screen. Also, if required, the bar chart can be saved as an image, just uncomment the line below in the above code:

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