title: DataTable find or if not found insert row
body: <p>I have a DataTable dt with 2 columns. First col (call it CustomerId) is unique and doesn't allow nulls. the second one allows nulls and is not unique.</p>
  
  <p>From a method I get a CustomerId and then I would like to either insert a new record if this CustomerId doesn't exist or increment by 1 what's in the second column corresponding to that CustomerId if it exists.</p>
  
  <p>I'm not sure how I should approach this. I wrote a select statement (which returns System.Data.DataRow) but I don't know how to test whether it returned an empty string.</p>
  
  <p>Currently I have:</p>
  
  <pre><code>//I want to insert a new row
  if (dt.Select("CustomerId ='" + customerId + "'") == null) //Always true :|
      {
          DataRow dr = dt.NewRow();
          dr["CustomerId"] = customerId; 
      }
  </code></pre>