title: "lookup" function of RDLC report isn't work in this case
body: <p>I have three related three dataset like these
  <a href="https://i.stack.imgur.com/dAMZU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dAMZU.png" alt="enter image description here"></a></p>
  
  <p>I need to display "INVOICE_CODE" from DatasetA concatenate with "COUNTRY_NAME" from DatasetC Example :</p>
  
  <pre><code>  "INV123-Korea"
  </code></pre>
  
  <p>I tried to use "Lookup" function by this step</p>
  
  <p>1.) First table is used for main table in a report.
   So I will assign DatasetA to my tablix1    </p>
  
  <p><a href="https://i.stack.imgur.com/fH0ql.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fH0ql.png" alt="enter image description here"></a></p>
  
  <p>2.) At Tablix1, rigth click on a cell and create expression via  </p>
  
  <p><a href="https://i.stack.imgur.com/ONEKX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ONEKX.png" alt="enter image description here"></a></p>
  
  <p>3.) Put this concept code. (A--->B--->C)</p>
  
  <pre><code>      =Lookup(A.FK,B.PK,    Lookup(C.FK,B.PK,C.ANS,"Dataset C") , "Dataset C")
  </code></pre>
  
  <p>But It's not work.</p>