c#

Question

i use these code to check for if a combobox and textbox is empty.

 

 

if(string.IsNullorWhiteSpace(textBox1.Text) && string.IsNullorEmpty(cmbcreditUnit.Text))

 

 

and it trigger is line of code.

 

listBox1.Items.Add(ComboBox1.SelectedItem);

 

 

 

by saying

Value cannot be Null,

Parameter name item.