Calling <code>ToString()</code> on an object should always return a string. Returning <code>null</code> instead contravenes the method's implicit contract.

== Noncompliant Code Example

----
public override string ToString ()
{
  if (this.collection.Count == 0) 
  {
    return null; // Noncompliant
  } 
  else 
  {
    // ...
  }
}
----

== Compliant Solution

----
public override string ToString () 
{
  if (this.collection.Count == 0) 
  {
    return string.Empty;
  } 
  else 
  {
    // ...
  }
}
----

include::../see.adoc[]