Google Charts in .Net

Introduction

Download Source Code.zip

Google Provided an open API for generating the charts which can be used in our commercial web applications. We can generate various graphs using the google chart api.

The Google Chart API lets you dynamically generate charts. To see the Chart API in action, open up a browser window and copy the following URL into it:

http://chart.apis.google.com/chart?cht=p3&chd=s:hW&chs=250x100&chl=Hello|World 
 

The following types of charts are available:

* Line Chart

* Bar Chart

* Pie Chart

* Venn diagram

* Scatter Plot

Following article demonstrates the usage of graph in asp.net

use the image tag and place the source there

<img src="http://chart.apis.google.com/chart?cht=p3&chd=s:asR&chs=400x150&chl=A|B|C" />

we can pass a variety of parameters to enhance the graph

the following are a few

Graph Title

we can place the chart title using

eg: chtt=Welcome chts

Graph Style

we can place the graph tile color and size of the font

chts for Title Style : color,size

eg: chts=225ff0,20

Graph Colors

we can have different colors

chco for colors: one or many

eg: chco=ff0000,00ff00,0000ff

Passing the Data

The Data can be passed using various encoding techniques like simple, text etc. I have done the simple encoding for you in C#

 public string GenerateGraph()
    {
        //Get the Data to draw the graph
        DataTable dt = new DataTable();
        dt = dtGraphData;

        //Get the max vals in the Data
        int maxval = GetMaxVal(dt);

        

        //SAMPLE: http://chart.apis.google.com/chart?cht=p3&chs=400x200&chd=s:asR&chl=A|B|C
        string GReqURL = "http://chart.apis.google.com/chart?chts="+GTitleColor+","+GTitleSize+"&chtt="+GTitle+"&chco="+GColors+"&cht=p3&chs="+GWidth+"x"+GHeight;

        //chts for Title Style : color,size
        //chtt for title text 
        //chco for colors: one or many


        string simpleEncoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        string chartData = string.Empty;
        string chartLabels = string.Empty;
        StringBuilder strbchartData = new StringBuilder();
        StringBuilder strbchartLabels = new StringBuilder();

        strbchartData.Append("&chd=s:");
        strbchartLabels.Append("&chl=");

        int strlen = simpleEncoding.Length - 1;
        foreach (DataRow dr in dt.Rows)
        {
            //Generate the chart DATA
            int arrVal = Convert.ToInt32(dr[2]);
            int len = strlen * arrVal / maxval;
            strbchartData.Append(simpleEncoding.Substring(len, 1));

            //Generate the Chart Labels
            strbchartLabels.Append(dr[1] + "|");
        }

        //Converting the string builder to string
        chartData = strbchartData.ToString();
        chartLabels = strbchartLabels.ToString();

        chartLabels = chartLabels.Substring(0, chartLabels.Length - 1);
        return GReqURL + chartData + chartLabels;
    }
    

The code is written in C#. You can assign all the properties you want to assign and finally call the GenerateGraph method which returns the string. The below is the code sample. The entire is article is explained using the PIE graph example. The remaining graphs can also be achieved using the same way.

        DataTable dt = new DataTable();
     //Get the Data the data table and pass it         dt = GetGraphData();                
        PieGraph pg = new PieGraph();
        pg.GraphColors = "5566AA";
        pg.GraphHeight="125";
        pg.GraphWidth="250";
        pg.GraphTitle = "Welcome to Test Graph";
        pg.GraphTitleColor = "112233";
        pg.GraphTitleSize = "20";
        pg.dtData = dt;

        GGReq = pg.GenerateGraph();
        
        
        this.DataBind();
    }

    DataTable GetGraphData()
    {
        SqlConnection con = new SqlConnection(connectionstring);
        SqlCommand cmd = new SqlCommand("Select * from GraphSupp", con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);
        return dt;
    } 

I took 3 cols id, description and the count and generated a string and assigned that to the image source.
this is to show how to pass data to the Pi graph, we can also perform simple encoding for other graphs too..

Steps for generation of the graph

1. Create a DataTable which contains column-2 as labels and column-3 as Data

2. Create and instance of PieGraph (refer the text doc i have attached)

3. Assign the properties

4. place the return string to the source of the image tag

5 Graph is generated

Points of Interest

1. Easy way of generation of graphs.

2. Less effort on the web server as there is no need to render the image using Drawing name space

3. Enhanced look and feel and open to all

References:

http://code.google.com/apis/chart/