title: how to map array/list and datatable/list c#
body: <p>I have an array/list now ["a","b","c","d","e","f"], and now I have a datatable dt:  </p>
  
  <pre><code>c1   c2  
   c   10  
   e   20  
  </code></pre>
  
  <p>I want to compare dt with the array and get back something as a result like  </p>
  
  <pre><code>a  0/null  
  b  0 /null  
  c  10  
  d  0/null  
  e  20  
  f  0/null  
  </code></pre>
  
  <p>I have no idea how to start with the mapping or whatever the procedure is, I tried a loop but I get <code>6*2 = 12</code> items
  Could anyone give some guidelines on how to do this?
  I tried to declare a boolean array,if i can find the element from A in dt, then add a true to the boolean array else add false. However i got 12 elements in boolean array instead of 6 and the position is all wrong</p>
  
  <pre><code> if (dt.Rows.Count &gt; 0)
          {
              for (int x = 0; x &lt; A.Length; x++)
              {
                  for (int t = 0; t &lt; dt.Rows.Count; t++)
                  {
                      string type = dt.Rows[t]["Sponsorship_Type"].ToString();
                      if (A[x] == type)
                      {
                          checks.Add(true);
                      }
                      else
                      {
                          checks.Add(false);
                      }
                  }
              }
          }
  </code></pre>