title: How to generate random numbers using C# that hasn't been listed in a database?
body: <p>I'm working on an application that allows me to generate random ID numbers (6 integers) for employees but I would like to know how to generate these random numbers using C# and not duplicate the numbers that has been already used by another employee in the SQL database. Below is the code done in SQL: </p>
  
  <pre><code>declare @unique_UID varchar(6)
  
  select @unique_UID = Right(ABS(CAST(CAST(NEWID() AS VARBINARY) AS INT)), 6)
  
  while exists (select 1 from dbo.tblUserID 
  
     where @unique_UID = UserID_UID 
           and len(@unique_uid) = 6
           and @unique_UID &lt;&gt; @parm_User_Pin)(
           select @unique_UID = Right(ABS(CAST(CAST(NEWID() AS VARBINARY) AS INT)), 6)
  </code></pre>
  
  <p>`</p>