title: Writing the content of a csv file to PostgreSQL with NPGSQL fails
body: <p>I am writing the Content of a csv file to a PostgreSQL table with help of NPGSQL in version 3.2.5.</p>
  
  <p>The content of my csv is the following</p>
  
  <pre><code>id, value
  1, 89
  2, 286
  3, 80
  4, 107
  </code></pre>
  
  <p>I use the following command to write </p>
  
  <pre><code>Using writer = conn.BeginTextImport("COPY tbl_test (id,value) FROM 'C:/temp/test.csv' DELIMITER ',' CSV HEADER")
  </code></pre>
  
  <p>When I run my code, the values are written into my database, but the command is throwing the following error message:</p>
  
  <pre><code>Received unexpected backend message CompletedResponse. Please file a bug.
  </code></pre>
  
  <p>When I run the command directly in the SQL Shell everything works fine, so the problem seems to be produced by NPGSQL. </p>
  
  <p>Here is my command which I use in the SQL Shell:</p>
  
  <pre><code>\COPY tbl_test(id,value) FROM 'C:/temp/test.csv' DELIMITER ',' CSV HEADER;
  </code></pre>
  
  <p>Has anybody else experience with this message?</p>