ComboBox data binding | 易学教程

问题

I have a combobox control on form that pull its data (Displays and values) from some datasource. On another side I have table with one row. I want when app is lauching, combobox set selectedvalue or selecteditem to value of one column in above row. And when user has changed combobox it will persist change to row. I have tried to bind SelectedValue to this column, but it doesn't work. Combobox just sets on start to first item. What is problem?

EDIT

This is a Win Forms project. Here is the binding code:

this.comboBoxCountries = new System.Windows.Forms.ComboBox();
this.countriesBindingSource = new System.Windows.Forms.BindingSource(this.components);

// 
// comboBoxCountries
// 
this.comboBoxCountries.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.searchCriteriaBindingSource, "Postcode", true));
this.comboBoxCountries.DataBindings.Add(new System.Windows.Forms.Binding("SelectedValue", this.searchCriteriaBindingSource, "CountryCode", true));
this.comboBoxCountries.DataSource = this.countriesBindingSource;
this.comboBoxCountries.DisplayMember = "Name";
this.comboBoxCountries.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
this.comboBoxCountries.FormattingEnabled = true;
this.comboBoxCountries.Location = new System.Drawing.Point(190, 19);
this.comboBoxCountries.Name = "comboBoxCountries";
this.comboBoxCountries.Size = new System.Drawing.Size(156, 21);
this.comboBoxCountries.TabIndex = 2;
this.comboBoxCountries.ValueMember = "Code";
this.comboBoxCountries.SelectedValueChanged += new System.EventHandler(this.comboBoxCountries_SelectedValueChanged);

// 
// countriesBindingSource
// 
this.countriesBindingSource.DataMember = "Countries";
this.countriesBindingSource.DataSource = this.dbDataSetCountries;
// 
// dbDataSetCountries
// 
this.dbDataSetCountries.DataSetName = "dbDataSetCountries";
this.dbDataSetCountries.SchemaSerializationMode = System.Data.SchemaSerializationMode.IncludeSchema;

// 
// searchCriteriaBindingSource
// 
this.searchCriteriaBindingSource.AllowNew = false;
this.searchCriteriaBindingSource.DataMember = "SearchCriteria";
this.searchCriteriaBindingSource.DataSource = this.dbDataSetSearchCriteria;
this.searchCriteriaBindingSource.BindingComplete += new System.Windows.Forms.BindingCompleteEventHandler(this.searchCriteriaBindingSource_BindingComplete);
// 
// dbDataSetSearchCriteria
// 
this.dbDataSetSearchCriteria.DataSetName = "dbDataSetSearchCriteria";
this.dbDataSetSearchCriteria.SchemaSerializationMode = System.Data.SchemaSerializationMode.IncludeSchema;

EDIT2

As I have mentioned in my comment below, I have another textbox that is binded to another DataMember of same binding source and textbox working fine. It's appear with appropriate value. When I change DataMember on same datamember on which I set selectedvalue property of combobox binding it's also show a good result and work properly.

Thanks in advance!

回答1:

Take a look at the DisplayMember and ValueMember properties of the combobox. You need to tell the ComboBox what member from the datasource to display in the drop down, and what value to give when SelectedValue is requested.

It sounds like your ComboBox is bound to a static list while your rows are not. You might consider using a BindingSource that you set the ComboBox and the DataGridView's DataSource to. That way when the DGV navigates to a new row, the ComboBox will be updated with the value for the new row.

Here is a link to the ComboBox on MSDN: http://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.aspx

回答2:

I find it out. So for managing with this issue you should remove SelectedValue databinding from visual studio data bound menu and put an appropriate code to add this databinding in some place after filling all bindingsources:

private void MainForm_Load_1(object sender, EventArgs e)
{
    this.searchCriteriaTableAdapter1.Fill(this.dbDataSetCountries.SearchCriteria);    

    this.searchCriteriaTableAdapter.Fill(this.dbDataSetSearchCriteria.SearchCriteria);    

    comboBoxCountries.DataBindings.Add("SelectedValue", this.dbDataSetCountries.SearchCriteria, "CountryCode");                
}

来源：https://stackoverflow.com/questions/8585243/combobox-data-binding

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data-binding

combobox