title: SQL Server Reporting Studio report showing "ERROR#" or invalid data type error
body: <p>I struggled with this issue for too long before finally tracking down how to avoid/fix it. It seems like something that should be on StackOverflow for the benefit of others.</p>
  
  <p>I had an SSRS report where the query worked fine and displayed the string results I expected. However, when I tried to add that field to the report, it kept showing "ERROR#". I was eventually able to find a little bit more info:</p>
  
  <blockquote>
    <p>The Value expression used in [textbox] returned a data type that is
    not valid.</p>
  </blockquote>
  
  <p>But, I knew my data was valid. </p>