The calling thread cannot access this object because a different thread owns it

Question

My code is as below

public CountryStandards() {     InitializeComponent();     try     {         FillPageControls();     }     catch (Exception ex)     {         MessageBox.Show(ex.Message, "Country Standards", MessageBoxButton.OK, MessageBoxImage.Error);     } }  /// <summary> /// Fills the page controls. /// </summary> private void FillPageControls() {     popUpProgressBar.IsOpen = true;     lblProgress.Content = "Loading. Please wait...";     progress.IsIndeterminate = true;     worker = new BackgroundWorker();     worker.DoWork += new System.ComponentModel.DoWorkEventHandler(worker_DoWork);     worker.ProgressChanged += new System.ComponentModel.ProgressChangedEventHandler(worker_ProgressChanged);     worker.WorkerReportsProgress = true;     worker.WorkerSupportsCancellation = true;     worker.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);     worker.RunWorkerAsync();                     }  private void worker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e) {     GetGridData(null, 0); // filling grid }  private void worker_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e) {     progress.Value = e.ProgressPercentage; }  private void worker_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) {     worker = null;     popUpProgressBar.IsOpen = false;     //filling Region dropdown     Standards.UDMCountryStandards objUDMCountryStandards = new Standards.UDMCountryStandards();     objUDMCountryStandards.Operation = "SELECT_REGION";     DataSet dsRegionStandards = objStandardsBusinessLayer.GetCountryStandards(objUDMCountryStandards);     if (!StandardsDefault.IsNullOrEmptyDataTable(dsRegionStandards, 0))         StandardsDefault.FillComboBox(cmbRegion, dsRegionStandards.Tables[0], "Region", "RegionId");      //filling Currency dropdown     objUDMCountryStandards = new Standards.UDMCountryStandards();     objUDMCountryStandards.Operation = "SELECT_CURRENCY";     DataSet dsCurrencyStandards = objStandardsBusinessLayer.GetCountryStandards(objUDMCountryStandards);     if (!StandardsDefault.IsNullOrEmptyDataTable(dsCurrencyStandards, 0))         StandardsDefault.FillComboBox(cmbCurrency, dsCurrencyStandards.Tables[0], "CurrencyName", "CurrencyId");      if (Users.UserRole != "Admin")         btnSave.IsEnabled = false;  }  /// <summary> /// Gets the grid data. /// </summary> /// <param name="sender">The sender.</param> /// <param name="pageIndex">Index of the page.( used in case of paging)   </pamam> private void GetGridData(object sender, int pageIndex) {     Standards.UDMCountryStandards objUDMCountryStandards = new Standards.UDMCountryStandards();     objUDMCountryStandards.Operation = "SELECT";     objUDMCountryStandards.Country = txtSearchCountry.Text.Trim() != string.Empty ? txtSearchCountry.Text : null;     DataSet dsCountryStandards = objStandardsBusinessLayer.GetCountryStandards(objUDMCountryStandards);     if (!StandardsDefault.IsNullOrEmptyDataTable(dsCountryStandards, 0) && (chkbxMarketsSearch.IsChecked == true || chkbxBudgetsSearch.IsChecked == true || chkbxProgramsSearch.IsChecked == true))     {         DataTable objDataTable = StandardsDefault.FilterDatatableForModules(dsCountryStandards.Tables[0], "Country", chkbxMarketsSearch, chkbxBudgetsSearch, chkbxProgramsSearch);         dgCountryList.ItemsSource = objDataTable.DefaultView;     }     else     {         MessageBox.Show("No Records Found", "Country Standards", MessageBoxButton.OK, MessageBoxImage.Information);         btnClear_Click(null, null);     } } 

The step objUDMCountryStandards.Country = txtSearchCountry.Text.Trim() != string.Empty ? txtSearchCountry.Text : null; in get grid data throws exception

The calling thread cannot access this object because a different thread owns it.

What's wrong here?

Answer 1

This is a common problem with people getting started. Whenever you update your UI elements from a thread other than the main thread, you need to use:

this.Dispatcher.Invoke(() => {     ...// your code here. }); 

You can also use control.Dispatcher.CheckAccess() to check whether the current thread owns the control. If it does own it, your code looks as normal. Otherwise, use above pattern.