Answer / Rahul Sagar

In ASP.NET, you can eliminate or prevent duplicate data across multiple tables by implementing unique constraints or primary keys at the database level and using SQL INNER JOINs with WHERE clauses to retrieve non-duplicate records. Here's an example of how to do that:

```csharpnstring connectionString = ConfigurationManager.ConnectionStrings["MyDb"].ConnectionString;
using (SqlConnection conn = new SqlConnection(connectionString))
{
conn.Open();

string query = "SELECT a.*, b.* FROM TableA AS a INNER JOIN TableB AS b ON a.Id = b.Id WHERE a.Id NOT IN (SELECT Id FROM TableC)";

using (SqlCommand cmd = new SqlCommand(query, conn))
{
using (SqlDataReader reader = cmd.ExecuteReader())
{
// Process the result set here
}
}
}```nThis example uses a SQL INNER JOIN to fetch data from TableA and TableB where Id is unique in both tables, but not present in TableC.

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