SqlDataReader - how to discover that column is empty

Question

I try to read the result of the query and discover if some of the columns is empty This is a way I started:

SqlDataReader rdr = cmd.ExecuteReader();
while (rdr.Read())
{
    rdr["ColumnName"]; // how do I know if it has a value or empty
}

I thought to do :

dr[4].ToString() == String.Empty

It makes a needed work, but I don`t like this (it is a hack rather than solution) can you advise me how do I do it correctly and elegantly?

Answer 1

Empty does not exists for int values and what is correct when working with databases is use Null which is the only true "Empty".

SqlDataReader rdr = cmd.ExecuteReader();
int colIndex = read.GetOrdinal("MyColumnName");

while (rdr.Read())
{
    // [true | false] your validation goes here!; 

    if (rdr.IsDBNull(colIndex)){
       //value is  null
    }
}

Please note that if you want use 0, "" or 1/1/1900 as empty values those will require a custom treatment.

Answer 2

This is how I do it

string UserInitialssql = rdr.IsDBNull(2) ? String.Empty : rdr.GetString(2);

If it is Int

Int32? i = rdr.IsDBNull(2) ? (Int32?)null : rdr2.GetInt32(2);

Answer 3

Another possibility is to use nullable types. e.g.:

SqlDataReader rdr = cmd.ExecuteReader();
while (rdr.Read())
{
    int? someNumber = rdr["ColumnName"] as int?;
    if (someNumber == null)
        // was NULL in database
    else 
       // use  someNumber.Value   to get int
}