how to read data from multiple csv files. filter then merge common data in another sql database asp.net ?

This is a pseudo code variant for how to do it

1. Open the file with e.g. StreamReader sr = File.OpenText()
2. In a loop read the file line by line with string line = sr.ReadLine()
3. Split the line into parts with string[] parts1 = line.Split(',')
4. Store the parts into a DataTable with the column names you want and RollNo as primary key
5. Repeat for file two and find an existing row using RollNo and update that row with Address.
6. Create SqlConnection and open the database
7. Create a SqlCommand object
8. Loop through the rows in the DataTable and get a DataRow dr for each row.
9. Create the SQL command string, like

String.Format("INSERT INTO MyTable ('RollNo', 'Name', 'Age', 'Address') VALUES ({0}, {1}, {2})", dr["RolNo"], dr["Name"], dr["Age"], dr["Address"]]);

10. Execute a non query
11. Repeat for next row


There are plenty of other ways to do it as well.

Search for
* How to read data from a comma separated file
* How to insert data into a SQL database