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When a duplicate import schema is encountered during compilation, System.xml may throw the following error message:
Item has already been added. Key in dictionary:"file:///C:/C.xsd" Key being added: "file:///C:/C.xsd"
In the previous error message, C:/C.xsd is the duplicate schema.
This hotfix cannot be applied on a system that is running the Microsoft .NET Framework 1.1 Service Pack 1. If you installed the .NET Framework 1.1 Service Pack 1 and are experiencing the symptoms that are described in this article, request the hotfix rollup package that is described in Microsoft Knowledge Base article 890673 to obtain a resolution. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
890673 Availability of the .NET Framework 1.1 Post-Service Pack 1 XML Web services and XML Messaging hotfix rollup package 8
Although this problem occurs in both the Microsoft .NET Framework 1.0 and in the .NET Framework 1.1, this resolution only applies to the .NET Framework 1.1.
To apply this hotfix, your computer must be running the .NET Framework 1.1.
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft .NET Framework 1.1 service pack that contains this hotfix.
To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:
Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.