How to use datareader with null values
c#, datareader, null
Solution
It seems to me that you need a conversion like this (using an extension method for convenience):
public static int? ToNullableInt32(this SqlInt32 value)
{
return value.IsNull ? (int?) null : value.Value;
}
Then:
Field2 = rdr.GetSqlInt32(Field2_Ordinal).ToNullableInt32()
(Comment on other answers: there's no need to bring `DbNull` into this, as `SqlInt32` can already represent null values. You just need to detect that before using `Value`.)
Problem
Say I have this class: ``` class myclass { public int Field1{ get; set; } public int? Field2 { get; set; } //Note Field2 is nullable } ``` I'm trying to populate a generic list with data coming from a database. As GetSqlInt32 implements INullable I would have thought that the below code would work. It doesn't. It generates an error if Field2 is null. ``` List<myclass> mylist=new List<myclass>(); int Field1_Ordinal = rdr.GetOrdinal("Field1"); int Field2_Ordinal = rdr.GetOrdinal("Field2"); SqlDataReader rdr = cmd.ExecuteReader(); //Execute a stored procedure to retrieve data from the database while (rdr.Read()) { mylist.Add(new myclass { Field1 = rdr.GetSqlInt32(Field1_Ordinal).Value, Field2 = rdr.GetSqlInt32(Field2_Ordinal).Value //Error if field2 is null }); } ``` Any ideas why it doesn't work?