Google Charts in .NET

• Download source code - 4.91 KB
• Download text doc - 4.17 KB

Introduction

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

The 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. Following are a few:

Graph Title

We can place the chart title using:

e.g.: chtt=Welcome chts

Graph Style

We can place the graph tile color and size of the font:

chts for Title Style : color,size

e.g.: chts=225ff0,20

Graph Colors

We can have different colors:

chco for colors: one or many

e.g.: 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. Below is the code sample. The entire article is explained using the PIE graph example. The remaining graphs can also be achieved using the same method.

    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...

Steps for Generation of the Graph

1. Create a DataTable which contains column-2 as labels and column-3 as Data
2. Create an instance of PieGraph (refer to 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/

History

• 20^th January, 2008: Initial post