Null safe way to get values from an IDataReader

Question

(LocalVariable)ABC.string(Name)= (Idatareader)datareader.GetString(0);

this name value is coming from database.. what happening here is if this name value is null while reading it's throwing an exception?

I am manually doing some if condition here. I don't want to write a manual condition to check all my variables..

I am doing something like this now..

string abc =  (Idatareader)datareader.GetValue(0);
if(abc = null)
    //assiging null
else
    assiging abc value

is there something like can we write extension method for this? thanks

Answer 1

Here is a couple extension methods that will nicely wrap up all of your concerns around retrieving strongly typed values from a data reader. If the value is DbNull the default of the type will be returned. In the case of string which is a class, a null will be returned. If the field was int, then 0 would be returned. Additionally, if you are expecting an int?, say from an nullable int field, null would be returned.

Specific Usage for Kumar's case:

string abc = datareader.GetValueOrDefault<string>(0);

General Usage

var name = GetValueOrDefault<string>(reader, "Name");

or

var name = reader.GetValueOrDefault<string>("Name");

or

var name = reader.GetValueOrDefault<string>(0);

Extension

public static class NullSafeGetter
{
   public static T GetValueOrDefault<T>(this IDataRecord row, string fieldName)
   {
       int ordinal = row.GetOrdinal(fieldName);
       return row.GetValueOrDefault<T>(ordinal);
   }

   public static T GetValueOrDefault<T>(this IDataRecord row, int ordinal)
   {
       return (T)(row.IsDBNull(ordinal) ? default(T) : row.GetValue(ordinal));
   }
}

from http://skysanders.net/subtext/archive/2010/03/02/generic-nullsafe-idatarecord-field-getter.aspx