Best way to check if column returns a null value (from database to .net application)

Question

I have a table with a DateTime column the column can have NULL values

Now I connect to the database using an ODBC connection and get the value into a DataTable in .net / c#.

I am able to check it for NULL by going

if(String.IsNullOrEmpty(table.rows[0][0].ToString())
{
     //Whatever I want to do
}

Is String.IsNullOrEmpty the correct way to check for null values.

Answer 1

Use DBNull.Value.Equals on the object without converting it to a string.

Here's an example:

   if (! DBNull.Value.Equals(row[fieldName])) 
   {
      //not null
   }
   else
   {
      //null
   }

Answer 2

row.IsNull("column")

Answer 3

Just check for

if(table.rows[0][0] == null)
{
     //Whatever I want to do
}

or you could

if(t.Rows[0].IsNull(0))
{
     //Whatever I want to do
}

Answer 4

System.Convert.IsDbNull(table.rows[0][0])

IIRC, the (table.rows[0][0] == null) won't work, as DbNull.Value != null

Answer 5

The prefered method would be to use DataRow.IsNull. It has some overrides which accept the column as an index, a name, or the DataColumn object.

Example using the column index:

if (table.rows[0].IsNull(0))
{
    //Whatever I want to do
}

And although the function is called IsNull it really compares with DbNull which is what you need (comparing with null won't work, that is why String.IsNullOrEmpty doesn't work)

And if you want something which isn't a DataRow to compare with DbNull you can always use Convert.IsDBNull.