dbnull

I have seen many, many versions of this on SO, but none of them seem to quite work for my needs. My data comes from a vendor database that allows null for DateTime fields. First I pull my data into a DataTable. using (SqlCommand cmd = new SqlCommand(sb.ToString(), conn)) using (SqlDataAdapter da = new SqlDataAdapter(cmd)) { da.Fill(dt); } I am converting a DataTable to a List<> for processing. var equipment = from i in dt.AsEnumerable() select new Equipment() { Id = i.Field<string>("ID"), BeginDate = i.Field<DateTime>("BeginDate"), EndDate = i.Field<DateTime>("EndDate"), EstimatedLife = i

I've always assumed that DbNull.value was a singleton. And thus you could do things like this: VB.NET: If someObject Is DbNull.Value Then ... End if C#: If (someObject == DbNull.Value) { ... } But recently, I serialised a DbNull instance using the XmlSerialiser and suddenly it wasn't a singleton any more. Type comparison operations (like C#'s (obj is DBNull)) work OK though. Code follows: [Serializable, System.Xml.Serialization.XmlInclude(typeof(DBNull))] public class SerialiseMe { public SerialiseMe() { } public SerialiseMe(object value) { this.ICanBeDbNull = value; } public Object

This question already has an answer here: How do I Parameterize a null string with DBNull.Value clearly and quickly 8 answers I have some textboxes on my page which can be empty because they are optional and I have this DAL code parameters.Add(new SqlParameter("@FirstName", FirstName)); parameters.Add(new SqlParameter("@LastName", LastName)); parameters.Add(new SqlParameter("@DisplayName", DisplayName)); parameters.Add(new SqlParameter("@BirthDate", BirthDate)); parameters.Add(new SqlParameter("@Gender", Gender)); Any of those fields can be empty. The problem is when they are empty I receive

sdr is my sqldatareader and I want to check that the curPrice value which is of type decimal is null. inrec.curPrice = sdr.IsDBNull(7) ? (decimal?)null : sdr.GetDecimal(7); This is the error message I am getting: Cannot implicitly convert type 'decimal?' to 'decimal'. An explicit conversion exists (are you missing a cast?) Where am I going wrong, please someone tell me. either convert curPrice to nullable, or use .Value property of nullable types. If curPrice is a property of a class then public decimal? curPrice { get; set; } decimal? indicates that it's a nullable decimal; you have to use

What are the benefits of using the c# method DataRow.IsNull to determine a null value over checking if the row equals DbNull.value? if(ds.Tables[0].Rows[0].IsNull("ROWNAME")) {do stuff} vs if(ds.Tables[0].Rows[0]["ROWNAME"] == DbNull.value) {do stuff} There is no real practical benefit. Use whichever one seems more readable to you. As to the particular differences between them, the basic answer is that IsNull queries the null state for a particular record within a column. Using == DBNull.Value actually retrieves the value and does substitution in the case that it's actually null. In other