title: Linq Query for dataset in c#?
body: <p>I have dataset which contains two tables like this:</p>
  
  <pre><code>DataTable dtFields = new DataTable("tmpFieldTable");
  
  dtFields.Columns.Add("FieldID");
  dtFields.Columns.Add("CDGroupID");
  dtFields.Columns.Add("CDCaption");
  dtFields.Columns.Add("fldIndex");
  
  DataTable dtCDGroup = new DataTable("tmpCDGroup");
  
  dtCDGroup.Columns.Add("CDGroupID");
  dtCDGroup.Columns.Add("Name");
  dtCDGroup.Columns.Add("Priority");
  
  DataSet ds = new DataSet("tmpFieldSet");
  
  ds.Tables.Add(dtFields);
  ds.Tables.Add(dtCDGroup);
  </code></pre>
  
  <p>How can I write following SQL query to LINQ</p>
  
  <pre><code>queryString = "Select FieldID, tmpCDGroup.Name, CDCaption, IIF(ISNULL(Priority),99,Priority), fldIndex from tmpFieldList LEFT OUTER JOIN tmpCDGroup ON tmpFieldList.CDGroupID = tmpCDGroup.CDGroupID order by 4,5 ";
  </code></pre>