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Data is Null. This method or property cannot be called on null values RRS feed

  • Question

  • Hi,

    I need some help with my program I am populating text boxes with data from a SQL Data BAse, but sometimes the values are "NULL" and so i get the following error : "Data is Null. This method or property cannot be called on null values"

    How can i write it so the reader ignores the null value and continues or puts in a blank??

    I am aware of IsDBNull function but am not sure how to implement it.

    any help greatly appreciated.

    Here is the code: 

    written in Visual Studio 2010 - Windows Form Application (c++) 

    private: System::Void listBoxCustomers_SelectedIndexChanged(System::Object^  sender, System::EventArgs^  e) {
    
    			 String^ ListBoxVal=listBoxCustomers->Text;
    
    			 String^ constring=L"datasource=127.0.0.1;port=3306;username=root;password=root";
    				 MySqlConnection^ conDataBase=gcnew MySqlConnection(constring);
    				 MySqlCommand^  cmdDataBase=gcnew MySqlCommand("select * from equipe.customers where name ='"+ListBoxVal+"';",conDataBase);
    				 MySqlDataReader^ myReader;
    
    				 try {
    					conDataBase->Open();
    					myReader=cmdDataBase->ExecuteReader();
    
    					if(myReader->Read()){
    
    							String ^ companyVal = myReader->GetString("company");
    							txtCompany -> Text = companyVal;
    
    							String ^ address1Val = myReader->GetString("address1");
    							txtAddress1 -> Text = address1Val;
    						
    							String ^ address2Val = myReader->GetString("address2");
    							txtAddress2 -> Text = address2Val;
    
    							String ^ cityVal = myReader->GetString("city");
    							txtCity -> Text = cityVal;
    
    							String ^ stateVal = myReader->GetString("state");
    							txtState -> Text = stateVal;
    
    							String ^ zipVal = myReader->GetString("zip");
    							txtZip -> Text = zipVal;
    
    							String ^ nameVal = myReader->GetString("name");
    							txtName -> Text = nameVal;
    				
    							String ^ idVal = myReader->GetString("id");
    							txtId -> Text = idVal;
    					}
    
    				 }	catch(Exception^ex){
    						MessageBox::Show(ex->Message);
    					}
    
    		 }

    Thanks,

    Ariel

    Tuesday, July 16, 2013 7:45 AM

Answers