In the XML content that is supplied for the column set column '%1!s!', the sqlDBType:base64Encoded attribute on the element ...

In the XML content that is supplied for the column set column '%1!s!', the sqlDBType:base64Encoded attribute on the element '%2!s!' is not valid. The base64Encoded attribute can only be used when the corresponding sparse column is of character data type (char, varchar, nchar, nvarchar), or if the sparse column is of data type sql_variant and the value of the xsi:type attribute is "Char", "VarChar", "NChar", or "NVarChar".