exception if combobox is not selected

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Hello. I want to know, how do I make an exception if the combobox is not selected. So far, it will come out Error: Object reference not set to an instance of an objet. If possible, I want it to come out like "Please select an item from the list." or something like that.

C#

string LabName = comboBoxLabNumber.SelectedItem.ToString();
string LabNumber = LabName;
string LabProblem = comboBoxProblem.SelectedItem.ToString();
string LabProb = LabProblem;

Or should I just do it using if/else? Any idea?

Thanks

Posted 22-Nov-10 21:18pm

Little Daffodil

Updated 22-Nov-10 21:21pm

JF2015

v3

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T.Saravanann · Accepted Answer · 2010-11-22T22:17:00

Solution 2

Hi,

using SelectedIndex for combobox.

if(comboBoxLabNumber.SelectedIndex > -1)
{
  LabName = comboBoxLabNumber.SelectedItem.ToString();
}
else
{
  MessageBox.Show("Please select an item!");
}

Try this way...

Cheers :)

Posted 22-Nov-10 22:17pm

T.Saravanann

Comments

Little Daffodil 23-Nov-10 5:08am

I tried this:

if (comboBoxLabNumber.SelectedIndex > -1 | comboBoxProblem.SelectedIndex > -1)
{
string LabName = comboBoxLabNumber.SelectedItem.ToString();
string LabNumber = LabName;

string LabProblem = comboBoxProblem.SelectedItem.ToString();
string LabProb = LabProblem;
}
else
{
MessageBox.Show("Please select an item!");
}

However, it comes out as error : The name 'LabName' and 'LabProblem' does not exist in the current context.

Toniyo Jackson 23-Nov-10 5:17am

Declare Strings outside the if condition....

Little Daffodil 23-Nov-10 5:24am

I'm blur. Does it mean this way?

if (comboBoxLabNumber.SelectedIndex > -1 | comboBoxProblem.SelectedIndex > -1)
{

}
else
{
MessageBox.Show("Please select an item!");
}

string LabName = comboBoxLabNumber.SelectedItem.ToString();
string LabNumber = LabName;

string LabProblem = comboBoxProblem.SelectedItem.ToString();
string LabProb = LabProblem;

Little Daffodil 23-Nov-10 5:27am

I tried this:

if (comboBoxLabNumber.SelectedIndex < 0 | comboBoxProblem.SelectedIndex <0)
{
MessageBox.Show("Please select the lab number and the problem");
}

string LabName = comboBoxLabNumber.SelectedItem.ToString();
string LabNumber = LabName;

string LabProblem = comboBoxProblem.SelectedItem.ToString();
string LabProb = LabProblem;

Yes, it works. However, this message of "Error: Object reference not set to an instance of an objet." still comes out.

T.Saravanann 23-Nov-10 5:47am

May be your problem occurred in second combobox because first you bind the first combo value and then second combo value. Are you call this condition in combobox selected index event means..try this code...

if(comboBoxLabNumber.SelectedIndex > 0)
{
LabName = comboBoxLabNumber.SelectedItem.ToString();
}
else
{
//LabName = string.Empty;
MessageBox.Show("Please select an item!");
}

if(comboBoxProblem.SelectedIndex > 0)
{
LabProblem = comboBoxProblem.SelectedItem.ToString();
}
else
{
//LabProblem = string.Empty;
MessageBox.Show("Please select an item!");
}

CPallini · Accepted Answer · 2010-11-22T21:41:00

Solution 1

Then handle the exception, for instance

C#

try
{
    LabName = comboBoxLabNumber.SelectedItem.ToString();
}
catch (Exception e)
{
    MessageBox.Show("Please select an item from the list");
    // here take the appropriate action.
}

Posted 22-Nov-10 21:41pm

CPallini

Updated 23-Nov-10 4:24am

v3

Comments

Dalek Dave 23-Nov-10 4:40am

Good Call.