Does the data cannot be empty when reading data with iDataReader?

nitian

I found some fields to appear when it comes: Data is Null. This Method or Property Cannot Be Called on Null Values.
Such an error! Don't know how you?

kalian2000

You can also read it empty, put your code out..

nitian

Omployed part, there are a lot of code, and apply this part of the reading.

Using (iDataReader Rdr = db.executeReader (DBCommand, Transaction)
                {
                    While (Rdr.Read ())
                    {
                        Csinfo CS = New Csinfo (Rdr.GetInt32 (0), Rdr.getstring (1), Rdr.Getint32 (2));
                        CSS.Add (CS);
                    }
                }

kalian2000

Is it because of the record you read, a field is empty, if it is empty, how can I "rdr.getint32 (0)."?

kalian2000

Let's make a judgment, if it is empty, give a default value:

Try ..

            Csinfo cs = new csinfo ((Rdr.IsDBNULL (0))? 0: (Rdr.Getint32 (0)), (Rdr.Indbnull (1))? "" "": (Rdr.getstring (1)), (RDR. ISDBNULL (2))? 0: (Rdr.Getint32 (2)));

nitian

What is "a field is empty"? Thank you

kalian2000

For example, a Student table, there are three fields (SNO, SNAME, SAGE)

One record

Sno Sname SAGE
111 NULL 21

IF (Rdr.Read ())
{
    IF (RDR.ISDBNULL (1))
    {
        // This record is not empty, but the SNAME field in the record is null ..
        // If there is an error with Rdr.getstring (1), because NULL cannot be converted to string ..
    }
}


I don't know if it is clear ..

nitian

Thank you, I understand.
Is there a better way to achieve this judgment? Because I have a lot of fields, this photo is too time.

charobin

The landlord does not read the value of iDataReader with rdr.getstring ().

For RDR [0] .toString ()
    Or column name RDR ["name"]. ToString () can read null values.