title: Why is DataView readonly despite "AllowEdit=true"?
body: <p>I have code (below) that I think should allow me to update the underlying tables, but I continue to get a "Underlying data is read only" error.</p>
  
  <p>In the code below, everything I've tried is included.  Clearly, I'm missing something!  A search in SO hasn't found clues... </p>
  
  <pre><code>APT.Columns["Selected"].ReadOnly = false;
  TWR.Columns["Selected"].ReadOnly = false;
  RWY.Columns["Selected"].ReadOnly = false;
  APT.Columns["Selected"].Expression = "false";
  TWR.Columns["Selected"].Expression = "false";
  RWY.Columns["Selected"].Expression = "false";
  // DataView with filtered "parent" table data
  // Apply user's filter for the "Fix"
  DataView dataView = new DataView(APT)
  {
      RowFilter = FixFilter(chkboxShowAll.Checked),
      Sort = "FacilityID",
      AllowEdit = true,
  };
  // RWY and TWR dont have ARTCC (filter item), 
  // so we can't filter by that, 
  // and "Join" makes the table readonly, 
  //so must grab root ID and change manually
  DataView dvTWR = new DataView(TWR)
  {
      AllowEdit = true                 // Enable editing
  };
  DataView dvRWY = new DataView(RWY)
  {
      AllowEdit = true
  };
  // TWRs and RWYs have the same ID as the APT, 
  // but not may have a TWY or RWY (e.g., Seabase)
  // This should update the "Selected" boolean 
  foreach (DataRowView dataRowView in dataView)
  {
      dataRowView.BeginEdit();
      dataRowView["Selected"] = true;  // *** &lt;- EXCEPTION HERE
      dataRowView.EndEdit();
      int result = dvRWY.Find(dataRowView["ID"]);
      if (result != -1)
      {
          dvRWY[result].BeginEdit();
          dvRWY[result]["Selected"] = true;
          dvRWY[result].EndEdit();
      }
      result = dvTWR.Find(dataRowView["ID"]);
      if (result != -1)
      {
          dvTWR[result].BeginEdit();
          dvTWR[result]["Selected"] = true;
          dvTWR[result].EndEdit();
      }
  }
  dvTWR.Dispose();        // Commit/close tables
  dvRWY.Dispose();
  </code></pre>
  
  <p>At the annotated code line, the exception fires:</p>
  
  <blockquote>
    <p>System.Data.ReadOnlyException: 'Column 'Selected' is read only.'</p>
  </blockquote>
  
  <p>Can anyone tell me the error of my ways?</p>