object reference not set to an instance of an object

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C#

DataSet ds = new DataSet();
            try
            {
                MySqlConnection con = new MySqlConnection("Server=localhost;UID=root;Database=db_cignal");
                con.Open();
                MySqlCommand command = con.CreateCommand();
                command.CommandText = "Select * from inventory where Product like @cb ";
                command.Parameters.Add("@cb", MySqlDbType.VarChar, 20).Value = "%" + cbProductDescription.SelectedItem.ToString();
                MySqlDataAdapter da = new MySqlDataAdapter();
                da.SelectCommand = command;
                da.Fill(ds);
                da.Update(ds);
                con.Close();

            }
            catch (Exception r)
            {
                MessageBox.Show(r.ToString());
            }

Posted 21-Feb-15 19:08pm

_bluRe_

Updated 21-Feb-15 23:24pm

Herman<T>.Instance

v2

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Abhinav S · Answer 1 · 2015-02-21T19:39:00

Solution 1

Debug your code. You are accessing a property of an object that is null.

Posted 21-Feb-15 19:39pm

Abhinav S

Comments

_bluRe_ 22-Feb-15 1:45am

yaa. the problem is here. cbProductDescription.SelectedItem.ToString(); even is i instantiate the selected value to a string, still same.

_bluRe_ 22-Feb-15 1:46am

i was trying to do a search here :)

Abhinav S 22-Feb-15 1:53am

SelectedItem is null aNd you are doing a toString() to that.

Try Convert.ToString() instead.

_bluRe_ 22-Feb-15 1:59am

still the same. i did something like this this.cbProductDescription.GetItemText(this.cbProductDescription.SelectedItem) no error but nothing happens as well

_bluRe_ 22-Feb-15 2:00am

DataSet ds = new DataSet();
try
{
MySqlConnection con = new MySqlConnection("connection...");
con.Open();
MySqlCommand command = con.CreateCommand();
command.CommandText = "Select * from inventory where Product like @cb ";
command.Parameters.Add("@cb", MySqlDbType.VarChar, 20).Value = "%" + this.cbProductDescription.GetItemText(this.cbProductDescription.SelectedItem);
MySqlDataAdapter da = new MySqlDataAdapter();
command.ExecuteNonQuery();
da.SelectCommand = command;
da.Fill(ds);
da.Update(ds);
con.Close();

}
catch (Exception r)
{
MessageBox.Show(r.ToString());
}

Tomas Takac 22-Feb-15 5:49am

First, do not post code in comments. Update your question using "improve question" link instead. Secondly, what does it mean, from business point of view, when there is nothing selected in cbProductDescription? Do you want to do the search anyway and return all products? Usually you want to have an item in the combo named e.g. "ALL" and make sure this is selected by default. Anyway, use good old "if" and test for cbProductDescription.SelectedItem being null and handle the situation properly.

_bluRe_ 22-Feb-15 2:01am

this is the updated code