Question

void ReadContent(string path)
{
  Contract.Requires(path!=null);
  string contentofileasstring = filehelperobj.GetContent(path);
   if(String.IsNullOrEmpty(contentofileasstring ))
  {
    throw new FileContentException(path + "No content found");
  }
  m_xmlobj = contentofileasstring ;
}

Is my assumption of the usage of code contracts and exceptions right in this case. Do you think it is logical to replace the exception with a code contract(or vice versa)?

code not tested.Just an example scenario

Answer 1

I would probably go for an implementation which looks like the following:

private void ReadContent(string path)
{
    Contract.Requires<FileMissingException>(File.Exists(path));
    string content = filehelperobj.GetContent(path);
    m_xmlobj = content;
}

Post Edit

As it’s the content you want to validate, I would put a Contract.Ensures(!String.IsNullOrEmpty(Contract.Result<string>())); inside the filehelperobj.GetContent(string) method. Then if the content being read was null or empty, I would throw an exception. e.g.

public string GetContent(string path)
{
    Contract.Requires<FileMissingException>(File.Exists(path));
    Contract.Ensures(!String.IsNullOrEmpty(Contract.Result<string>()));

    using(var reader = new StreamReader(File.OpenRead(path)))
    {
        var content = reader.ReadToEnd();

        if(String.IsNullOrEmpty(content))
            throw new FileContentException("No content found at file: " + path);

        return content;
    }
}