DataSet column can be NULL but not converted to string ?

Question

I have a string which can be empty if its not empty it is containing a xml document. The problem is null values are allowed in this dataset column of DataType System.String.

Error Message:this.MetaData' threw an exception of type 'System.Data.StrongTypingException'

base {System.SystemException} = {"The value for column 'MyData' in table 'GMyTAbleName' is DBNull."}

UPDATE

here is a screenshot of the cause:

http://666kb.com/i/bld3eelnaicsgb9tv.png

you see how it tries to convert NULL to a string which should be returned.

That code is from the DataSet.Designer.cs file, how could I change that behaviour? :S

Answer 1

Consider testing the column first using the IsNull method on the DataRow.

I've never did like DBNull. :)

Answer 2

ok I made it working. I will list the steps here:

1.) http://msdn.microsoft.com/en-us/library/ya91ataz(vs.71).aspx

choose this: (Empty) To have null values return as String.Empty.

2.) As we now a string.empty is not a valid xml-string I checked this in the getter of my appropriate property.

private XmlDocument XMLMyData
 {
    get
    {
        XmlDocument doc = new XmlDocument();    

        if (this.MyData.Trim().Length > 0) 
            doc.LoadXml(this.MyData); // return xml-string in the xml document
        else if (String.IsNullOrEmpty(this.MyData)) 
            return doc;             // return empty xml document

        return doc;                                     
    }
}