bool fireAgain = true;
IDTSComponentMetaData100 myMetaData;
myMetaData = this.ComponentMetaData;
myMetaData.FireInformation(0, "SubComponent", "Description", string.Empty, 0, ref fireAgain);

http://msdn.microsoft.com/en-us/library/ms136031.aspx

The Script Component raises errors, warnings, and informational messages by using the methods of the **IDTSComponentMetaData100** interface returned by the **ComponentMetaData** property.

Raising Events in an SSIS Script Component

C#