DataSet and Validation XML Error

[Peter]

I have a problem. I create a file XSD "file1" that contains
simpletypes and complextypes, generate the dll,
import the dll in a different XSD "file2" (of an other project).
In a DataSet validate xml by "file2", but it generate the following
exception:

Type 'Prova.Attribute.att:complexType1' is not declared. An error
occurred at file:///C:/Documents and ........

The code C# that I used is:

DataSet dataCollectDataSet = new DataSet ();
StringReader xmlStringReader = new StringReader (xmlString);

string dataCollectXsd = @"C:\Documents and Settings\......\file2.xsd";

dataCollectDataSet.ReadXmlSchema (strReaderXsd);
dataCollectDataSet.ReadXml (xmlStringReader, XmlReadMode.ReadSchema);

Help me!!