How can i identify whether the value from the database is null or not in .Net 2.0?

I am fetching the data from the database and populate it into the domain object.Lets say

    public class A
    {
        int? ai;

        public int? AI
        {
            get { value = ai;}
            Set { ai = value; }

        }

    }

so i am creating the domain object in the main class.

    class TestClass
    {
        static void Main(string[] args)
        {
            class A objData = new A();
    // here some logic for creating connection to the database and calling the datareader to fetch the //data.
        int temp =(int) objDataReader["aiDAta"];
        objData.ai = temp == null? 0: temp;
        func(objData);

     }
    }

public void func(A objData)
{

// Here i want to display the value of  objData.ai only if its database value is not null.since i was   //already assigned 0,if the value from the database is null...how can i able to identify whether the value  //from the database is null or not? also,In database "aiDAta" will have the value range from 0 - 99.
}

}

Here i want to display the value of objData.ai only if its database value is not null.since i was already assigned 0,if the value from the database is null...how can i able to identify whether the value from the database is null or not? also,In da开发者_开发百科tabase "aiDAta" will have the value range from 0 - 99.

---

Compare objData.ai to

DBNull.value

instead of NULL

or

check

IsDBNull(objData.ai)

or

public Int32 TryCastInteger32(object value)
{
    if (value != null && !Information.IsDBNull(value)) {
        Int32 retVal = default(Int32);
        if (Int32.TryParse(value.ToString(), out retVal)) {
            return retVal;
        }
    }
    return 0;
}

---

If your casting to a Nullable checked the HasValue property. It will be true only is the value type is not null.

---

Usually null DB fields are returned as System.DbNull in which case the following cast will fail:

int temp =(int) objDataReader["aiDAta"]; 

You can use DBDataReader's IsNull method to check for a null value before using it

---

alternatively you could also just let the database validate if the value is null or not by creating an oracle function and passing the value you want it to evaluate:

CREATE OR REPLACE
  FUNCTION isNull(
      i_value IN VARCHAR2)
    RETURN NUMBER
  IS
  BEGIN
    IF i_value IS NOT NULL THEN
      RETURN 1;
    ELSE
      RETURN 0;
    END IF;
  END;
  /