Use the same form to search data for many forms

Question

Hi fellows please help me on this..... here is my code. I use one form to search data to != forms using 'visible' validation but i find this error.  NullReferenceException was unhandled Object reference not set to an instance of an object. in one of the form needing data..... public string IDSet { set { tb_IdFunc.Text = value; } } public string NomeSet { set { lbNomeFunc.Text = value; } } private void bt_Search_Click(object sender EventArgs e) { if (tb_IdFunc.Text == ) { frmSearchFunc SF = new frmSearchFunc(); SF.Location = new System.Drawing.Point(CG.parameterXLocation() CG.parameterYLocation()); SF.ShowDialog(); } else { FuncDal.shearchFaltaID(this.lstFalta this.dtDataFalta.Value.Month this.dtDataFalta.Value.Year Convert.ToInt32(this.tb_IdFunc.Text)); this.lbNomeFunc.Text = FuncDal.getFuncNam(this.tb_IdFunc.Text); } } In search form..... private void lstSearchFuncGeral_DoubleClick(object sender EventArgs e) { //frmAtribuirFalta atribF = new frmAtribuirFalta(); frmAtribuirFalta atribF = (frmAtribuirFalta)Application.OpenForms[frmAtribuirFalta]; configSubsidio cnfgSubs = (configSubsidio)Application.OpenForms[configSubsidio]; try { if (atribF.Visible == true) { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); //nomeProp = arrayDetail[0].ToString().Trim() +   + arrayDetail[17].ToString().Trim(); atribF.IDSet = dadosID; atribF.NomeSet = dadosNome; } } catch (Exception ex) { throw ex; } try { if (cnfgSubs.Visible == true) { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); cnfgSubs.IDSet = dadosID; cnfgSubs.NomeSet = dadosNome; } } catch (Exception ex) { throw ex; } this.Close(); } Regards!

Sousa Pambo · Answer

Hi Vulpes Still the same nothing has changed. I'll find another way to get data. I'll keep searching a solution but now I have to keep working in my project it will work anyway. Thanks a lot. I'll keep asking....be fine!

Vulpes · Answer

Well as mentioned earlier as long as an instance of the frmAtribuirFalta is currently open it can't be atribF that's null. Even if weren't open you'd get an exception when you tried to cast to frmAtribuirFalta and the code is progressing beyond that point. So to try and pin-point what is null I'd put in a MessageBox.Show: if (atribF.Visible == true) // no message until here { string message = null; if (FuncDal == null) message = Funcdal is null; else if (this.lstSearchFuncGeral.FocusedItem == null) message = FocusedItem is null); else if (this.lstSearchFuncGeral.FocusedItem.SubItems[0] == null) message = SubItems[0] is null); if (message != null) { MessageBox.Show(message); return; } else { MessageBox.Show(None of the three is null!); } arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); // shows the null message here // etc } If FuncDal is a class name rather than a variable then omit the first 'if' statement otherwise it won't compile.

Sousa Pambo · Answer

Hi Vulpes I did as u said I used the break-point the result...can see the bolded lines I can't analyse it. I don't whether the error is the first bolded line or the second... private void lstSearchFuncGeral_DoubleClick(object sender EventArgs e) { //frmAtribuirFalta atribF = new frmAtribuirFalta(); //configSubsidio cnfgSubs = new configSubsidio(); frmAtribuirFalta atribF = (frmAtribuirFalta)Application.OpenForms[frmAtribuirFalta]; configSubsidio cnfgSubs = (configSubsidio)Application.OpenForms[configSubsidio]; try { if (atribF.Visible == true) // no message until here { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); //it shows the null message here //nomeProp = arrayDetail[0].ToString().Trim() +   + arrayDetail[17].ToString().Trim(); atribF.IDSet = dadosID; atribF.NomeSet = dadosNome; } } catch (NullReferenceException nre) { MessageBox.Show(nre.Message); } try { if (cnfgSubs.Visible == true) { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); cnfgSubs.IDSett = dadosID; cnfgSubs.NomeSett = dadosNome; } } catch (NullReferenceException nre) { MessageBox.Show(nre.Message); } this.Close(); } Thanks!

Vulpes · Answer

To make any progress with this we have to figure out what's null as it's far from obvious. What I'd suggest is that you put a break-point on the first line of the method and then 'single step' through it hovering your mouse over the variables as you go until you find one that's null.

Sousa Pambo · Answer

Hi vulpes! now i'm really lost. Is there a way to solve this problem? Or I'll have to use one search form to each form needing data.... what do you suggest?

Vulpes · Answer

I doubt whether that's the problem. Application.OpenForms will only get a reference to the forms if they've already been instantiated and are currently open. Otherwise it will return null and when you attempt to cast to the actual form type a null reference exception will be thrown. However this exception will be thrown BEFORE the first try block is even reached and so won't be caught at all.

Sousa Pambo · Answer

Hi Vulpes I think I got the point. I used catch (NullReferenceException nre) { MessageBox.Show(nre.Message); } for this way it shows the error after keep works normally. Then I used ... frmAtribuirFalta atribF = new frmAtribuirFalta(); instead... //frmAtribuirFalta atribF = (frmAtribuirFalta)Application.OpenForms[frmAtribuirFalta]; it works for another form but this one doesn't get data from search form. I think the point is... I have to instanciate the forms but doing that it won't get the data from the search data form

Vulpes · Answer

If you uncomment the first block of code does the MessageBox pop up twice or just the once?

Sousa Pambo · Answer

the message: Object Reference not set to an instance of an object

Vulpes · Answer

Instead of re-throwing the exception with; throw ex; try just printing out the error message: MessageBox.Show(ex.Message);

Sousa Pambo · Answer

Hi Vulpes When I comment the line ..... (I bolded those line) it works but it doesn't accept when its more than one. I don't get the conflict here. private void lstSearchFuncGeral_DoubleClick(object sender EventArgs e) { //frmAtribuirFalta atribF = new frmAtribuirFalta(); //frmAtribuirFalta atribF = (frmAtribuirFalta)Application.OpenForms[frmAtribuirFalta]; configSubsidio cnfgSubs = (configSubsidio)Application.OpenForms[configSubsidio]; //try //{ // if (atribF.Visible == true) // { // arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); // //nomeProp = arrayDetail[0].ToString().Trim() +   + arrayDetail[17].ToString().Trim(); // atribF.IDSet = dadosID; // atribF.NomeSet = dadosNome; // } //} //catch (Exception ex) //{ // throw ex; //} try { if (cnfgSubs.Visible == true) { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); cnfgSubs.IDSet = dadosID; cnfgSubs.NomeSet = dadosNome; } } catch (Exception ex) { throw ex; } this.Close(); }

Vulpes · Answer

A couple of possibilities: If FuncDal is an object reference rather than a class name perhaps that could be null. If there is currently no focused item in the ListView then this.lstSearchFuncGeral.FocusedItem will be null.

Sousa Pambo · Answer

Hi Vulpes Please see the bolded comment private void lstSearchFuncGeral_DoubleClick(object sender EventArgs e) { //frmAtribuirFalta atribF = new frmAtribuirFalta(); frmAtribuirFalta atribF = (frmAtribuirFalta)Application.OpenForms[frmAtribuirFalta]; configSubsidio cnfgSubs = (configSubsidio)Application.OpenForms[configSubsidio]; try { if (atribF.Visible == true) { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); //nomeProp = arrayDetail[0].ToString().Trim() +   + arrayDetail[17].ToString().Trim(); atribF.IDSet = dadosID; atribF.NomeSet = dadosNome; } } catch (Exception ex) { throw ex; // the error is pointing here although I double_click to other form } try { if (cnfgSubs.Visible == true) // I'm trying to get data from this form { arrayDetail = FuncDal.FuncAllData(this.lstSearchFuncGeral.FocusedItem.SubItems[0].Text); cnfgSubs.IDSet = dadosID; cnfgSubs.NomeSet = dadosNome; } } catch (Exception ex) { throw ex; } this.Close(); }

Vulpes · Answer

Can you pinpoint on which line the error occurs?