how to check if a datareader is null or empty

Question

I have a datareader that return a lsit of records from a sql server database. I have a field in the database called "Additional". This field is 50% of the time emp

Answer 1

I haven't used DataReaders for 3+ years, so I wanted to confirm my memory and found this. Anyway, for anyone who happens upon this post like I did and wants a method to test IsDBNull using the column name instead of ordinal number, and you are using VS 2008+ (& .NET 3.5 I think), you can write an extension method so that you can pass the column name in:

public static class DataReaderExtensions
{
    public static bool IsDBNull( this IDataReader dataReader, string columnName )
    {
        return dataReader[columnName] == DBNull.Value;
    }
}

Kevin

Answer 2

AMG - Sorry all, was having a blond moment. The field "Additional" was added to the database after I had initially designed the database.

I updated all my code to use this new field, however I forgot to update the actual datareader code that was making the call to select the database fields, therefore it wasn't calling "Additional"

Answer 3

@Joe Philllips

SQlDataReader.IsDBNull(int index) requires the ordinal number of the column. Is there a way to check for nulls using Column Name, and not it's Ordinal Number?

Answer 4

This

Example:

objCar.StrDescription = (objSqlDataReader["fieldDescription"].GetType() != typeof(DBNull)) ? (String)objSqlDataReader["fieldDescription"] : "";

Answer 5

if (myReader["Additional"] != DBNull.Value)
{
    ltlAdditional.Text = "contains data";
}
else
{
     ltlAdditional.Text = "is null";
}

Answer 6

Try this simpler equivalent syntax:

ltlAdditional.Text = (myReader["Additional"] == DBNull.Value) ? "is null" : "contains data";