nullreferenceexception

问题 In my Dispose methods (like the one below), everytime i want to call someObj.Dispose() i also have a check for someObj!=null. Is that because of bad design on my part? Is their a cleaner way to ascertain that Dispose of all the members (implementing IDisposable) being used in an object is called without having a risk of NullReference exception ? protected void Dispose(bool disposing) { if (disposing) { if (_splitTradePopupManager != null) { _splitTradePopupManager.Dispose(); } } } Thanks for

问题 When I run the code below I get this error NullreferenceException was unhandled.. below is my code private void showScannerDialog() { this.scanner = null; this.imageItem = null; this.getScanner(); WIA.CommonDialog dialog = new WIA.CommonDialog(); Items imageItems = dialog.ShowSelectItems(this.scanner, WiaImageIntent.TextIntent, WiaImageBias.MinimizeSize, false, true, false); if (imageItems != null) { foreach (Item item in imageItems) { imageItem = item; break; } } } thanks // complete code

问题 I have following classes. class Tim { public Tim() { } public Tom GetTom() { return new Tom(); } } class Tom { public Tom() { } public Jim GetJim() { return new Jim(); } } class Jim { public Jim() { } public Jom GetJom() { return null; } } class Jom { public Jom() { } public string GetMagicString() { return "Hello World"; } } Its used as follows. class Program { static void Main(string[] args) { new Tim().GetTom().GetJim().GetJom().GetMagicString(); } } When I run it, a Null Reference

问题 I've been using the same bit of code for several versions of my app with no problems, but I'm now mysteriously receiving NullRerefenceException s with the following: this.Loaded += delegate { deleteBrush = new DeleteBrushAdorner( background ); AdornerLayer al = AdornerLayer.GetAdornerLayer( background ); al.Add( deleteBrush ); // null ref here?? }; background is just a Border element. My two thoughts on what could be causing it are a) switching to .NET 4.0, and b) placing instances of the

问题 I've been using the same bit of code for several versions of my app with no problems, but I'm now mysteriously receiving NullRerefenceException s with the following: this.Loaded += delegate { deleteBrush = new DeleteBrushAdorner( background ); AdornerLayer al = AdornerLayer.GetAdornerLayer( background ); al.Add( deleteBrush ); // null ref here?? }; background is just a Border element. My two thoughts on what could be causing it are a) switching to .NET 4.0, and b) placing instances of the

问题 This is a weird one, and I'm at a loss to understand what's going on here. I have a web api project that in one controller a call to a certain method eventually calls a function in a service that looks like this: public MyClassBase GetThing(Guid id) { if (cache.ContainsKey(id)) { return cache[id]; } else { var type = typeof(MyClassBase).Assembly.GetTypes().FirstOrDefault ( t => t.IsClass && t.Namespace == typeof(MyClassBase).Namespace + ".Foo" && t.IsSubclassOf(typeof(MyClassBase)) && (t

问题 I'm checking the cell values of cells of a column that might or not be empty/null so I needed something to avoid a NullReferenceException . How do I do that since even with the IsNullOrWhiteSpace() and IsNullOrEmpty() I get that exception somehow. Here's part of the code I'm using: s = "Total = " + dataGridView1.Rows[0].Cells.Count + "0 = " + dataGridView1.Rows[0].Cells[0].Value.ToString() + "/n 1 = " + dataGridView1.Rows[0].Cells[1].Value.ToString() + "/n 2= " + dataGridView1.Rows[0].Cells[2

问题 I'm checking the cell values of cells of a column that might or not be empty/null so I needed something to avoid a NullReferenceException . How do I do that since even with the IsNullOrWhiteSpace() and IsNullOrEmpty() I get that exception somehow. Here's part of the code I'm using: s = "Total = " + dataGridView1.Rows[0].Cells.Count + "0 = " + dataGridView1.Rows[0].Cells[0].Value.ToString() + "/n 1 = " + dataGridView1.Rows[0].Cells[1].Value.ToString() + "/n 2= " + dataGridView1.Rows[0].Cells[2

问题 This question already has answers here : What is a NullReferenceException, and how do I fix it? (29 answers) Closed 5 years ago . I was having some issues the other day with my interface lagging and after asking here someone suggested using a using statement to dispose of the webbrowser. Now after implementing it I keep getting: NullReferenceException was unhandled by user code- Object reference not set to an instance of an object. I am having a weird issue because even if I am running code

问题 i got answer to my last problem related to my mini project: when i tried to update image control from other thread i got error: Trying to update image control source from other tread and getting Error- enter link description here but now i got NullReferenceException at this line: item.Dispatcher.Invoke(new Action(() => image1.Source = item)); from some reason and i dont know why? the code: public partial class MainWindow : Window { BlockingCollection<BitmapSource> pictures = new