VARCHAR treated as NVARCHAR

   Here's a more recent example of a custom provider helper which is able to detect column information.  The example below detects Xml data types and excludes columns of this type from parameter mapping for insert/update/delete statements.

public class CustomProviderHelper : IdeaBlade.Rdb.SqlServerProviderHelper {

   // Reset ALL strings to Ansi strings for select/insert/update/delete parms

   public override System.Data.DbType MapDbParameterType(System.Data.DbType pDbType) {

     return pDbType == System.Data.DbType.String ? System.Data.DbType.AnsiString : pDbType;

   }

   // This is called by the RdbAdapterProvider when building insert/update/delete statements.

   // We have enough column information here to detect XML types, and reset the parameter.DbType.

   public override void QualifyParameter(System.Data.IDbDataParameter pParameter, System.Data.DataRow pSchemaRow) {

     // Do base logic

     base.QualifyParameter(pParameter, pSchemaRow);

     // This was typed as an ansi string by MapDbParameter, reset to correct Xml datatype.

     if ((Type)pSchemaRow["ProviderSpecificDataType"] == typeof(System.Data.SqlTypes.SqlXml)) {

        pParameter.DbType = System.Data.DbType.Xml;

     }

     // There may be other useful schema info here too - like pSchemaRow["DataTypeName"]

   }

}