问题描述
更新：
我还没有找到真正的原因，但是我发现，更新任何其他数据绑定控件的属性都会引发Folder-Combobox中的“ delayed”事件。 到目前为止，这不是一个干净的解决方案，但我通过更新未使用的财产来帮助自己。也就是说，直到我了解真正的原因为止。
原始帖子：
我目前正在研究Windows.Forms项目（不幸的是必须是WinForms），并且我有三个ComboBoxes，每个DataSource都绑定到一个List。列表包含文件夹或文件名。 每个组合框的SelectedItem属性也都绑定到一个字符串。 SelectedValueChanged事件已注册并实现。
它们彼此依赖，所以当我更新combobox1的数据源时，combobox2的数据源也必须更新。这是因为在combobox1中，您可以为文件选择一个子目录，然后在combobox2中列出这些文件。
现在是问题所在。有时会发生，当我以编程方式更新combobox1中的SelectedItem时，SelectedValueChanged事件没有立即触发。程序继续，直到combobox2的数据源更新为止。仅然后，将执行combobox1的SelectedValueChanged事件方法，但不幸的是，它“太迟了”，因为combobox2的数据源已使用combobox1的错误子目录进行了更新。
我想了解，没有立即触发该事件。下面，我发布了相关代码部分的简短示例。
// Cmb1Data and Cmb2Data are the String-Lists which are bound to the DataSource property of the ComboBoxes
// TempCmb1(2)SelectedValue is a string value which contains the value which is to be set.
// Cmb1(2)SelectedValue is a string which is bound the the SelectedItem property of the ComboBoxes
List<string> TempCmb1Data = MainVM.GetCmb1Data();
// some if-statement (plausibility check) is done here before the DataSource is updated.
Cmb1Data = TempCmb1Data ;
if (Cmb1Data.Contains(TempCmb1SelectedValue)
Cmb1SelectedValue = TempCmb1SelectedValue; // This should fire the event - but sometimes it does not...
List<string> TempCmb2Data = MainVM.GetCmb2Data();
// as before,some if-statement (plausibility check) is done here before the DataSource is updated.
Cmb2Data = TempCmb2Data; // This is the point,where the SelectedValueChangedEvent of Combobox1 suddenly is fired,followed by the SelectdValueChanged event of Combobox 2
我仔细检查了所有数据绑定和事件方法注册，它们都可以。如果我手动更改SelectedItem，一切也都可以正常运行-只是有时必须以编程方式完成。
先谢谢您。 啊
编辑：
因此，我将代码总结到了相关部分中（如下所述）。当我测试此代码以确保它正确时，没有发生此问题。在我看来，问题隐藏在其他地方，而且不知道在哪里，因此在这里发布的代码太多了。如果发现问题，我将再次深入查看并发布更新。
public partial class Form
{
RuntimeData _RuntimeData = new RuntimeData();
private void Form_Load(object sender,EventArgs e)
{
AddDataBindings();
}
private void AddDataBindings()
{
cmbFolders.DataBindings.Add("SelectedItem",_RuntimeData,"SelectedFolder");
cmbFolders.DataBindings.Add("DataSource","Folders");
cmbFiles.DataBindings.Add("SelectedItem","SelectedFile");
cmbFiles.DataBindings.Add("DataSource","Files");
}
bool _ToggleFlag = false;
private void btTest_Click(object sender,EventArgs e)
{
string TcpString = "Cmd=Execute;Dir=SubDirName1;File=FileName1.dat;";
if (_ToggleFlag)
TcpString = "Cmd=Execute;Dir=SubDirName2;File=FileName2.dat;";
_ToggleFlag = !_ToggleFlag;
// Method is usually executed in separate thread but the problem exists either way. So Threading removed for simplification
ParseAndExecute(TcpString,_RuntimeData);
}
private void ParseAndExecute(string tcpString,RuntimeData runtimeData)
{
if (String.IsNullOrEmpty(tcpString))
return;
string[] Elements = tcpString.Split(new char[] { ';','=' },StringSplitOptions.RemoveEmptyEntries);
// Replaced GetFolders-Method for simplification
List<string> TempFolders = new List<string>() { "SubDirName1","SubDirName2","SubDirName3" };
if (TempFolders [0] == Elements[3])
;//runtimeData.ProcessFolderChange = true;
runtimeData.Folders.Clear();
runtimeData.Folders = TempFolders;
if (runtimeData.Folders.Contains(Elements[3]))
{
if (runtimeData.Folders[0] != Elements[3])
;//runtimeData.ProcessFolderChange = true;
runtimeData.SelectedFolder = Elements[3];
}
// Replaced GetFiles-Method for simplification
List<string> TempFiles = new List<string>() { "FileName1.dat","FileName2.dat","FileName3.dat" };
if (TempFiles [0] == Elements[5])
;//runtimeData.ProcessFileChange = true;
runtimeData.Files.Clear();
runtimeData.Files = TempFiles;
if (runtimeData.Files.Contains(Elements[5]))
{
if (runtimeData.Files[0] != Elements[5])
;//runtimeData.ProcessFileChange = true;
runtimeData.SelectedFile = Elements[5];
}
}
private void cmbFolders_SelectedValueChanged(object sender,EventArgs e)
{
//if (!_RuntimeData.ProcessFolderChange)
//return;
//_RuntimeData.ProcessFolderChange = false;
((ComboBox)sender).DataBindings["SelectedItem"].WriteValue();
_RuntimeData.Files.Clear();
_RuntimeData.Files = new List<string>() { "FileName1.dat","FileName3.dat" };
}
private void cmbFiles_SelectedValueChanged(object sender,EventArgs e)
{
//if (!_RuntimeData.ProcessFileChange)
//return;
//_RuntimeData.ProcessFileChange= false;
((ComboBox)sender).DataBindings["SelectedItem"].WriteValue();
// do some random stuff with the file...
}
}
// Relevant data from RuntimeData class.
public class RuntimeData : VMBase
{
private List<string> folders = new List<string>() { "SubDirName1","SubDirName3" };
public List<string> Folders
{
get { return folders; }
set
{
folders = value;
OnPropertyChanged(new PropertyChangedEventArgs("Folders"));
}
}
private List<string> files = new List<string>() { "FileName1.dat","FileName3.dat" };
public List<string> Files
{
get { return files; }
set
{
files = value;
OnPropertyChanged(new PropertyChangedEventArgs("Files"));
}
}
string selectedFolder = String.Empty;
public string SelectedFolder
{
get { return selectedFolder ; }
set
{
selectedFolder = value;
OnPropertyChanged(new PropertyChangedEventArgs("SelectedFolder"));
}
}
string selectedFile = String.Empty;
public string SelectedFile
{
get { return selectedFile ; }
set
{
selectedFile = value;
OnPropertyChanged(new PropertyChangedEventArgs("SelectedFile"));
}
}
}
public abstract class VMBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (PropertyChanged != null)
PropertyChanged(this,e);
}
}
解决方法
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