hello!
i had the following line in my program
_dataRow["field"] = SqlString.Null;
_dataRow is of type DataRow and the associated field is of type varchar.
after saving this change, the column in my database has value "Null"
instead of the 'real' NULL!
you could then get the row by executing
SELECT * FROM mytable WHERE field = 'Null'
and not by
SELECT * FROM mytable WHERE field IS NULL
isn't that strange?
table:
create table DBTEST (timecode datetime, strfield varchar(100))
where column timecode is defined as primary key.
this is my testapp:
using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
namespace DBProblem
{
public class DBProblem
{
public static int Main(string[] args)
{
// DB connection
SqlConnection Connection = new SqlConnection("Server
=;Database=;User ID=;Password=;Application Name=dbproblem");
Connection.Open();
// Dataset befüllen
SqlCommand Command = new SqlCommand("insert into DBTEST
(timecode, strfield) values (@timecode, @strfield)", Connection);
Command.Parameters.Add(new SqlParameter("@timecode",
SqlDbType.DateTime));
Command.Parameters["@timecode"].Value = DateTime.Now;
Command.Parameters.Add(new SqlParameter("@strfield",
SqlDbType.VarChar));
Command.Parameters["@strfield"].Value = SqlString.Null;
Command.ExecuteNonQuery();
// row was inserted with column strfield containing NULL
Command = new SqlCommand("select * from DBTEST",
Connection);
SqlDataAdapter _DataAdapter = new SqlDataAdapter(Command);
SqlCommandBuilder _CommandBuilder = new SqlCommandBuilder
(_DataAdapter);
DataSet _DataSet = new DataSet();
_DataAdapter.Fill(_DataSet, "DBTEST");
DataRow _DataRow = _DataSet.Tables["DBTEST"].Rows[0];
_DataRow["strfield"] = SqlString.Null;
_DataAdapter.Update(_DataSet, "DBTEST");
// now, column strfield of first row contains "Null"
Connection.Close();
return 0;
}
}
}
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