C#

benson.misi wrote:

Object cannot be cast from DBNull to other types.
what does this mean

if(row["blah"]==null)

if (row["blah"] == DBNull.Value)

[System.Xml.Serialization.XmlTypeAttribute(Namespace = "http://namespace/", TypeName = "person")]
public class Person
{
   private string _name;
   
   [System.Xml.Serialization.XmlElementAttribute(ElementName = "name")]
   public string Name { get { return _name; } }
}

using System;
using System.Runtime.Serialization;
using Person;

namespace SchoolPackage
{
    [Serializable()]
    public class Student : ISerializable
    {
        private Person person;
        private int intReference;
        private int intReqTypeID;
        //
        private string strLastAlteredByUser;
        private DateTime dteAlteredDate;
        private Boolean blnIsDirty;
        private Boolean blnIsNew;
        private enum RequestType : int
        {
            Create = 1, Delete = 2, Update = 3, Execute = 4,
            Retrieve = 5, RetrieveMultiple = 6
        }

        public Student(Person person, String user, int TypeID, int Reference) 
        {
            this.person = person;
            this.strLastAlteredByUser = user;
            this.dteAlteredDate = DateTime.Now;
            this.blnIsDirty = false;
            this.blnIsNew = true;
            this.intReqTypeID = TypeID;
            this.intReference = Reference;
        }
      
        //Deserialization constructor.
        public Student(SerializationInfo info, StreamingContext ctxt)
        {
            //Get the values from info and assign them to the appropriate properties
            person = (Person)info.GetValue("person", typeof(Person));
            action = (string)info.GetValue("action", typeof(string));
            intReference = (int)info.GetValue("intReference", typeof(int));
            intReqTypeID = (int)info.GetValue("intReqTypeID", typeof(int));
        }
                
        //Serialization function.
        public void GetObjectData(SerializationInfo info, StreamingContext ctxt)
        {            
            info.AddValue("person", person);
            info.AddValue("action", action);
            info.AddValue("intReference", intReference);
            info.AddValue("intReqTypeID", intReqTypeID);
        }

}

using System;
using System.Runtime.Serialization;
using Person;
using System.Xml;
using System.Xml.Serialization;

namespace SchoolPackage
{
    //This line is basically all you need for the class to be serializable
    [System.Xml.Serialization.XmlTypeAttribute(Namespace = "http://www.x.com/namespace/", TypeName = "Student")]
    public class Student
    {
        [System.Xml.Serialization.XmlElementAttribute(ElementName = "myCustomXmlElementName")]
        public string StrLastAlteredByUser
        {
            get { return strLastAlteredByUser; }
            set { strLastAlteredByUser = value; }
        }
    }
}

using System;
using System.Collections;
using System.Xml.Serialization;
using System.Xml;

namespace Data.Package
{
    [System.Xml.Serialization.XmlTypeAttribute(Namespace = "Data.Package", TypeName = "Changes")]
    public class Changes
    {
        private Boolean blnIsDirty;
        private Boolean blnIsNew;
  
        public Changes() 
        {
            this.blnIsDirty = false;
            this.blnIsNew = true;
        }

        [System.Xml.Serialization.XmlElementAttribute(ElementName = "IsDirty")]
        public Boolean IsDirty
        {
            get { return blnIsDirty; }

            set { blnIsDirty = value; }
        }

        [System.Xml.Serialization.XmlElementAttribute(ElementName = "IsNew")]
        public Boolean IsNew
        {
            get { return blnIsNew; }

            set { blnIsNew = value; }
        }
    }
}

using System;
using System.Text;
using System.Xml.Serialization;
using System.IO;
using System.Xml;

namespace Helper
{
    public class Serializer
    {
        public Serializer() 
        { 
        
        }

        /// <summary>
        /// Method to convert a custom Object to XML string
        /// </summary>
        /// <param name="pObject">Object that is to be serialized to XML</param>
        /// <returns>XML string</returns>
        public String serializeObject(Object pObject)
        {
            try
            {
                String XmlizedString = null;
                MemoryStream memoryStream = new MemoryStream();
                XmlSerializer xs = new XmlSerializer(pObject.GetType());
                XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.UTF8);
                xs.Serialize(xmlTextWriter, pObject);
                memoryStream = (MemoryStream)xmlTextWriter.BaseStream;
                XmlizedString = UTF8ByteArrayToString(memoryStream.ToArray());
                return XmlizedString;
            }
            catch (Exception e)
            {
                System.Console.WriteLine(e);
                return null;
            }
        } 
        
        /// <summary>
        /// Method to reconstruct an Object from XML string
        /// </summary>
        /// <param name="pXmlizedString"></param>
        /// <returns></returns>
        public Object deserializeObject(String pXmlizedString)
        {
            XmlSerializer xs = new XmlSerializer(typeof(Object));
            MemoryStream memoryStream = new MemoryStream(StringToUTF8ByteArray(pXmlizedString));
            XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.UTF8);
            return xs.Deserialize(memoryStream);
        } 

        /// <summary>
        /// To convert a Byte Array of Unicode values (UTF-8 encoded) to a complete String.
        /// </summary>
        /// <param name="characters">Unicode Byte Array to be converted to String</param>
        /// <returns>String converted from Unicode Byte Array</returns>
        private String UTF8ByteArrayToString(Byte[] characters)
        {
            UTF8Encoding encoding = new UTF8Encoding();
            String constructedString = encoding.GetString(characters);
            return (constructedString);
        }
        
        /// <summary>
        /// Converts the String to UTF8 Byte array and is used in De serialization
        /// </summary>
        /// <param name="pXmlString"></param>
        /// <returns></returns>
        private Byte[] StringToUTF8ByteArray(String pXmlString)
        {
            UTF8Encoding encoding = new UTF8Encoding();
            Byte[] byteArray = encoding.GetBytes(pXmlString);
            return byteArray;
        } 
    }
}