I am showing a screenshot of all records of an EMP_DETAIL table so that it can become easy to understand.
Now, create an ASP.NET web application -> create a DropDownList control, one GridView control, and two SqlDataSources. Your form will look like the following figure.
Now we specify a DataSouce for both SqlDataSources. Follow the given steps.
Step 1: Click on the smart tag of SqlDataSource1.
Step 2: Click on Configure Data Source.
Step 3: A new window will be opened to choose a data connection.
Step 4: Click the New Connection button. A new window will be opened. Write the server name, user name, password, and select your database. Look at the following figure.
Step 5: Click the ok button. You will be presented with the Configure DataSource wizard. Click the "Next" button. A new window will be opened and it will ask to save the connection string.
Step 6: Select the Database table and then choose column names by checking the checkboxes.
Step 7: Then click the Next button, then the Finish button.
Step 8: Now it's time for SqlDataSource2. Repeat step 1 to step 6. At the 6th step choose all columns by checking all checkboxes.
Step 9 : Click the Where button. Select Column ( At which basis you want to show record. I have selected "E_ID" ) -> Select operator ( I have selected "=" ) -> Select source ( I have selected "Control" ) -> Select DropDownList1 ( Or ID of DropDownList ) for Control ID.
Step 10: Click the Add button. Then click the ok button. After this, you will reach the Configure Data Source wizard; click the Add button, then click the Finish button.
Step 11: Select DropDownList and click at smart tab -> Click at "Choose Data Source". A new window will be opened. Choose Data Source, Select column to display and another column which will be the value of the DropDownList then click the ok button.
Step 12: Select GridView and click at smart tag -> Choose Data Source - SqlDataSource2.
Step 13: Select DropDownList and set its AutoPostBack property to "True".
Run the application.
Select another name from DropDownList. Like I am selecting an employee name "Rajesh Tripathi".