title: C# Datatable.select fails with # hash character in data
body: <p>I have a datatable containing a list of service calls placed each month. Column F4 contains the serial number of the machine, now all I wanted to do was find the number of service calls placed for each serial number and add the count to a new a column. I wrote the code below and all was working fine but then a problem arose when a hash sign '#' appeared in the data to reflect an unknown or yet assigned serial number. This caused the error "Cannot perform '=' operation on System.String and System.Int32." on the line "DataRow[] FoundRow = dt.Select("[F4] ="  + chkStr);
  The F4 column is a text/string and I even tried cloning the datatable and manually assigning the column to .DataType = typeof(String); I know its the # sign giving the issue as if I remove from the data for testing purposing all is fine. Can anyone shed some light on this. Many thanks.</p>
  
  <pre><code>// datatable dt contains all my monthly call data
  dt.Columns.Add("Counter", typeof(System.Int32)); // add a count column to the datatable            
  
  for (int i = 0; i &lt; dt.Rows.Count; i++) //loop through the datatable
  {
  string chkStr = dt.Rows[i]["F4"].ToString(); // get 1st serial num, then each other one in loop
  DataRow[] FoundRows = dt.Select("[F4] ="  + chkStr); // OK now select all the table rows containing this serial, place in FoundRows               
  Int32 count = FoundRows.Length; // get the length which is a count of the same serial num / service calls                
  dt.Rows[i]["Counter"] = count;
  }
  </code></pre>