How to find out common element(s) in two generic list by LINQ, LINQ Set Operations

int[] twos = { 2, 4, 6, 8, 10 };

int[] threes = { 3, 6, 9, 12, 15 };

// 6

var intersection = twos.Intersect(threes);

// 2, 4, 8, 10

var except = twos.Except(threes);

// 2, 4, 7, 8, 10, 3, 9, 12, 15

var union = twos.Union(threes);

Understand SQL Injection by code

If put the following string in the SSN text box

' ; DROP DATABASE pubs  --

Using the input, the application executes the following stored procedure, which internally executes a similar SQL statement.

SqlDataAdapter myCommand = new SqlDataAdapter(

                                "LoginStoredProcedure '" +

                                 SSN.Text + "'", myConnection);

The code INJECT into the user's malicious input and generates the following query.

SELECT au_lname, au_fname FROM authors WHERE au_id = ''; DROP DATABASE pubs --'

 

Reference: 

How To: Protect From SQL Injection in ASP.NET

http://msdn.microsoft.com/en-us/library/ff648339.aspx