Merge Two Datatable Columns and Bind to ComboBox Control

Introduction

In this article, let us see how to bind a ComboBox with various columns from various datatables.

For example, I have a datatable "Server" with columns "server" and "database". Another datatable "server1" with columns "servername" and "databasename". Now I want to display all the values in the server and servername columns into a single ComboBox.

Using the code

1. Create a new Windows application. Add a ComboBox control.
2. I have 2 XML files to dump into datasets:

   XML File 1
   
   <?xml version="1.0" standalone="yes" ?>
   -<NewDataSet>
   -<Table1>
   <Server>Server1</Server>
   <Database>Database1</Database>
   </Table1>
   -<Table1>
   <Server>Server2</Server>
   <Database>Database2</Database>
   </Table1>
   -<Table1>
   <Server>Server3</Server>
   <Database>Database3</Database>
   </Table1>
   </NewDataSet>

   XML File 2
   
   <?xml version="1.0" standalone="yes" ?>
   -<NewDataSet>
   -<table2>
   <ServerName>Server4</ServerName>
   <DatabaseName>Database4</DatabaseName>
   </table2>
   -<table2>
   <ServerName>Server5</ServerName>
   <DatabaseName>Database5</DatabaseName>
   </table2>
   -<table2>
   <ServerName>Server6</ServerName>
   <DatabaseName>Database6</DatabaseName>
   </table2>
   </NewDataSet>
   

3. Now in the form_load, add the following code. I am going to merge 2 datatables from 2 datasets. Then going to create a new column in the merged dataset and fill the new column with values from both datatables. See the commented lines for more explanation and a better understanding.
   
   privatevoid Form1_Load(object sender, EventArgs e)
   {

   DataSet ds = newDataSet();

   string path = "C:\\XMLFile1.xml";

   //Read XMLFILE1.XML and save it in ds

   ds.ReadXml(path);

   path ="C:\\XMLFile2.xml";

   DataSet ds2 = new DataSet();

   //Read XMLFILE2.XML and save it in ds2

   ds2.ReadXml(path);

   //Merge datatable from both datasets

   ds.Tables[0].Merge(ds2.Tables[0]);

   //add new column "All Servers"

   ds.Tables[0].Columns.Add("All Servers", typeof(string));

   //Read datatable and fetch all server and dump it into new column "All servers"

   foreach (DataRow dr in ds.Tables[0].Rows)

   {

   dr["All Servers"] = dr["server"].ToString();

   }

   //Read datatable and fetch all servername and dump it into new column "All servers"

   foreach (DataRow dr in ds.Tables[0].Rows)

   {

   //When we merged 2 datatables if there are 3 rows in datatable 1 and 2 in datatable2

   //now it will become 5rows,So am checking if its blank, then fill it with servername column from datatable2(initial)

   if (dr["All Servers"] == "")

   dr["All Servers"] = dr["servername"].ToString();

   }

   //Bind the datatable

   comboBox1.DataSource = ds.Tables[0];

   //set displaymember as "All servers", the newly created column.

   comboBox1.DisplayMember = "All Servers";
   
   }
   

4. Now run the application and check the ComboBox; you will have all the servers listed inside the ComboBox:
   
   
   

I have attached the complete source code also.