Today I needed to save a fully populated dataset as xml to my drive in order to simplfly unit testing.  I thought this would be pretty straight forward, but as it turns out it was not.  There is one little wrinkle that may bite you if you are not careful.  Below I will describe what I tried and why it failed and finally what worked.

Problem: I need to save a fully populated Dataset as XML to disk

Solution Attempt 1: Use DataSet.WriteXml( LocationOnDisk )

This worked, mostly.  I was able to get the XML document and reload it into a a dataset using DataSet.ReadXml( LocationOnDisk ).  A problem arose because one of my columns was always null.  And by default simply doing a WriteXml does not save schema information. More information on this here.

Solution Attempt 2: Use DataSet.WriteSchema (LocationOnDisk) then user DataSet.WriteXml( LocationOnDisk)

 This worked.  By saving my schema information for the dataset I am later able to repopulate the data and have my null values replaced.  In order to do this all you have to do is the following.

DataSet ds = new DataSet();
ds.ReadXmlSchema( XsdFileLocation );
ds.ReadXml( XmlFileLocation );

I know this seems pretty trival, but If you do not understand how Xml and schemas work you could spin your wheels for a while trying to figure out why your column/data was not repopulated.

Hope this helps someone,

Till next time,

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