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Setting DropDownList SelectedItem

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DropDownList

This is a migrated thread and some comments may be shown as answers.

25 Answers, 1 is accepted

Accepted

answered on 22 Jul 2010, 11:55 AM

Hi Steve,

Thank you for writing.

Currently if you use the code that Ramius provided you will notice that an InvalidOperationException is thrown. This is because when an item is created with the new operator, it has not yet been added to the Items collection and its Owner property will return null. When you set the SelectedItem property and if the value's Owner is different than the drop down list element's, it will throw an exception.

You can select an item by string by calling the FinsString() method with the desired string, then assign the result to SelectedIndex (FindString() returns an int). In order to avoid writing this code every time you can abstract it away in an extension method if you are using .NET Framework 3.0 or later. Here is how your code could look like:

Define the extender class

public static class RadDropDownListExtender

{

public static void SelectByText(this RadDropDownList dropDown, string searchItem)

{

dropDown.SelectedIndex = dropDown.FindString(searchItem);

}

Use it wherever you need

this.radDropDownList1.SelectByText("MyItem");

We will consider adding a property to RadDropDownList so that it support this functionality out of the box.
Please write again if you have other questions.

Greetings,
Victor
the Telerik team

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answered on 10 Aug 2010, 12:59 PM

Hi.

Am I right that DropDownList is not offering any set of SelectedValue by Design time anymore.

I switched my first Form now from RadComboBox to RadDropDownList and I am missing a lot of features.

Let me describe:

We have a list of objects e.g. the Language, meaning Language_ID and Language_Name.

So the RadComboBox DataSource was the BindingSource filled with a list of Language Objects.

On the other hand we have the so called "mother" object which is e.g. the Customer Object. The customer object is also
bound to a BindingSource. So what was really nice fancy behavior in RadComboBox i was able to set the SelectedValue
property in DataBinding to "customerBindingSource.Language", meaning if the customerObject was filled and the Language
was already set the corresponding RadComboBox with a List of all possible Languages was correctly set.
Also a change of the Language was directly affecting the Object property change of customer.language.

Please tell me if i had overseen something or this is features are not part of the DropDownList control anymore.

Think of we have a lot of controls, of course also a lot of RadComboBox controls. Changing those to DropDownList
not having above mentioned functionality will cause a lot of workload.

Thanks in advance.

All the best.

Adrian.

answered on 19 May 2015, 10:50 AM

I tried this:

public partial class MyDropDownList : RadDropDownList

{

...

public void SelectByText( string searchItem)
{
RadDropDownListExtender.SelectByText(this, searchItem);
}
}

public static class RadDropDownListExtender
{
public static void SelectByText(this RadDropDownList dropDown, string searchItem)
{
dropDown.SelectedIndex = dropDown.FindString(searchItem);
// dropDown.SelectedText = searchItem;
}
}

... and in my dialog form:

RadListDataItem item = new RadListDataItem();
item = ddl.Items.First();

ddl.SelectByText(item.Text);

and the selected text stays empty. What do I wrong?

answered on 20 May 2015, 08:58 AM

330630.zip

Hello Wesley,

Thank you for writing.

I have tested this and on my side your code is working properly. For convenience I prepared a small sample, based on the information that you provided so far and attached it to this thread. Could you please check it and let me know how it differs from your real setup?

Additionally, I wanted to ask you what is the exact version of the suite that you are currently using?

I am looking forward to your reply.

Regards,
Dimitar
Telerik

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answered on 05 Apr 2016, 10:11 AM

Hi.

I have some bug with SelectedItem binding in 2016.1.216 version - value of bound object is not changing, when SelectedIndex changed. Initial value is displayed correctly.

Here is simple example.

public enum State

{

Work = 0,

Idle = 1,

Maintenance = 2

}

public class Entity

{

public int Id { get; set; }

public State State { get; set; }

}

public partial class Form1 : RadForm

{

private Entity _entity;

public Form1()

{

InitializeComponent();

StartPosition = FormStartPosition.CenterScreen;

_entity = new Entity {Id = 1, State = State.Idle};

bindingSource.DataSource = _entity;

}

private void radButton1_Click(object sender, System.EventArgs e)

{

if ((State) radDropDownList1.SelectedIndex != _entity.State)

RadMessageBox.Show(string.Format("Selected index is {0}, but entity State value is {1}.\nWhy?",

radDropDownList1.SelectedIndex, (int) _entity.State), "Error");

}

partial class Form1

{

/// <summary>

/// Required designer variable.

/// </summary>

private System.ComponentModel.IContainer components = null;

/// <summary>

/// Clean up any resources being used.

/// </summary>

/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>

protected override void Dispose(bool disposing)

{

if (disposing && (components != null))

{

components.Dispose();

}

base.Dispose(disposing);

}

#region Windows Form Designer generated code

/// <summary>

/// Required method for Designer support - do not modify

/// the contents of this method with the code editor.

/// </summary>

private void InitializeComponent()

{

this.components = new System.ComponentModel.Container();

Telerik.WinControls.UI.RadListDataItem radListDataItem1 = new Telerik.WinControls.UI.RadListDataItem();

Telerik.WinControls.UI.RadListDataItem radListDataItem2 = new Telerik.WinControls.UI.RadListDataItem();

Telerik.WinControls.UI.RadListDataItem radListDataItem3 = new Telerik.WinControls.UI.RadListDataItem();

this.radSpinEditor1 = new Telerik.WinControls.UI.RadSpinEditor();

this.radLabel1 = new Telerik.WinControls.UI.RadLabel();

this.radLabel2 = new Telerik.WinControls.UI.RadLabel();

this.radDropDownList1 = new Telerik.WinControls.UI.RadDropDownList();

this.radButton1 = new Telerik.WinControls.UI.RadButton();

this.bindingSource = new System.Windows.Forms.BindingSource(this.components);

((System.ComponentModel.ISupportInitialize)(this.radSpinEditor1)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this.radLabel1)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this.radLabel2)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this.radDropDownList1)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this.radButton1)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this.bindingSource)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this)).BeginInit();

this.SuspendLayout();

//

// radSpinEditor1

//

this.radSpinEditor1.DataBindings.Add(new System.Windows.Forms.Binding("Value", this.bindingSource, "Id", true));

this.radSpinEditor1.Location = new System.Drawing.Point(63, 13);

this.radSpinEditor1.Name = "radSpinEditor1";

this.radSpinEditor1.Size = new System.Drawing.Size(100, 20);

this.radSpinEditor1.TabIndex = 0;

this.radSpinEditor1.TabStop = false;

//

// radLabel1

//

this.radLabel1.Location = new System.Drawing.Point(12, 14);

this.radLabel1.Name = "radLabel1";

this.radLabel1.Size = new System.Drawing.Size(16, 18);

this.radLabel1.TabIndex = 1;

this.radLabel1.Text = "Id";

//

// radLabel2

//

this.radLabel2.Location = new System.Drawing.Point(12, 54);

this.radLabel2.Name = "radLabel2";

this.radLabel2.Size = new System.Drawing.Size(32, 18);

this.radLabel2.TabIndex = 2;

this.radLabel2.Text = "State";

//

// radDropDownList1

//

this.radDropDownList1.DataBindings.Add(new System.Windows.Forms.Binding("SelectedIndex", this.bindingSource, "State", true));

this.radDropDownList1.DropDownStyle = Telerik.WinControls.RadDropDownStyle.DropDownList;

radListDataItem1.Text = "Work";

radListDataItem2.Text = "Idle";

radListDataItem3.Text = "Maintenance";

this.radDropDownList1.Items.Add(radListDataItem1);

this.radDropDownList1.Items.Add(radListDataItem2);

this.radDropDownList1.Items.Add(radListDataItem3);

this.radDropDownList1.Location = new System.Drawing.Point(63, 52);

this.radDropDownList1.Name = "radDropDownList1";

this.radDropDownList1.Size = new System.Drawing.Size(125, 20);

this.radDropDownList1.TabIndex = 3;

//

// radButton1

//

this.radButton1.Location = new System.Drawing.Point(170, 114);

this.radButton1.Name = "radButton1";

this.radButton1.Size = new System.Drawing.Size(110, 24);

this.radButton1.TabIndex = 4;

this.radButton1.Text = "Save";

this.radButton1.Click += new System.EventHandler(this.radButton1_Click);

//

// bindingSource

//

this.bindingSource.DataSource = typeof(DropDownListBinding.Entity);

//

// Form1

//

this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);

this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;

this.ClientSize = new System.Drawing.Size(292, 144);

this.Controls.Add(this.radButton1);

this.Controls.Add(this.radDropDownList1);

this.Controls.Add(this.radLabel2);

this.Controls.Add(this.radLabel1);

this.Controls.Add(this.radSpinEditor1);

this.Name = "Form1";

//

this.RootElement.ApplyShapeToControl = true;

this.Text = "Form1";

((System.ComponentModel.ISupportInitialize)(this.radSpinEditor1)).EndInit();

((System.ComponentModel.ISupportInitialize)(this.radLabel1)).EndInit();

((System.ComponentModel.ISupportInitialize)(this.radLabel2)).EndInit();

((System.ComponentModel.ISupportInitialize)(this.radDropDownList1)).EndInit();

((System.ComponentModel.ISupportInitialize)(this.radButton1)).EndInit();

((System.ComponentModel.ISupportInitialize)(this.bindingSource)).EndInit();

((System.ComponentModel.ISupportInitialize)(this)).EndInit();

this.ResumeLayout(false);

this.PerformLayout();

}

#endregion

private Telerik.WinControls.UI.RadSpinEditor radSpinEditor1;

private Telerik.WinControls.UI.RadLabel radLabel1;

private System.Windows.Forms.BindingSource bindingSource;

private Telerik.WinControls.UI.RadLabel radLabel2;

private Telerik.WinControls.UI.RadDropDownList radDropDownList1;

private Telerik.WinControls.UI.RadButton radButton1;

}