Unable to cast object of type System.DBNull to type System.String

Question

In my database I have 6 columns, all of them allow null values. I want to make a simple form with an updating feature.

Product , SNO ,BTCH Expiry ,QTY ,RATE and Amount.

I get an exception:

Unable to cast object of type 'System.DBNull' to type 'System.String'

Here is my code :

int a = dataGridView1.CurrentCell.RowIndex;

            try
            {

                using (AmdDataSet.Test_ibrahimDataTable table = new AmdDataSet.Test_ibrahimDataTable())
                {

                  int b = a+1;
                    using (AmdDataSetTableAdapters.Test_ibrahimTableAdapter adp = new AmdDataSetTableAdapters.Test_ibrahimTableAdapter())
                    {
                        adp.GetDataBySNO(a);
                         AmdDataSet.Test_ibrahimRow erow;
                        erow = table.NewTest_ibrahimRow();
                        lblSNO.Text = erow.SNO.ToString();
                        txtProduct.Text= erow.PRODUCTS;
                        txtExpiry.Text = erow.EXPIRYDATE.ToShortDateString();
                        txtBatchNo.Text = erow.BATCHNO.Trim().ToString();

                    }
                }
            }
            catch (Exception ex)
            {
                lbleror.Text = ex.Message;
            }

score 5 · Accepted Answer · answered May 17 '12 at 07:55

5

Try this

lblSNO.Text = (erow.SNO == null) ? string.Empty : erow.SNO.ToString()

or

lblSNO.Text = (erow.SNO == DBNull.Value) ? string.Empty : erow.SNO.ToString()

answered May 17 '12 at 07:55

Blachshma

17,097
4
58
72

2

Actually the second option will work – Emad Mokhtar May 17 '12 at 11:16
lblSNO.Text = (erow.SNO == DBNull.Value) ? string.Empty : erow.SNO.ToString() it is Showing Cannot be applied of Type int – ebbicsku May 17 '12 at 13:58
What is the type of SNO column in the DB? – Blachshma May 28 '12 at 10:08
These didn't work for me.. I had to use the Is[PropertyName]Null() method of the dataset property. – Chuck D Oct 18 '17 at 02:59

score 3 · Answer 2 · edited May 23 '17 at 11:48

3

Have a look at this similar example for handling DBNulls

edited May 23 '17 at 11:48

Community

1
1

answered May 17 '12 at 08:09

Ebad Masood

2,389
28
46

score 2 · Answer 3 · answered May 17 '12 at 07:55

2

Before calling ToString method call Convert.IsDBNull to check if value is not null.

answered May 17 '12 at 07:55

Marek Dzikiewicz

2,844
1
22
24

Unable to cast object of type System.DBNull to type System.String

3 Answers3