Setting dropdownlist selecteditem programmatically

问题:

I want to set the selecteditem attribute for an ASP.Net dropdownlist control programmatically.

So I want to pass a value to the dropdownlist control to set the selected item where the item is equal to the passed value.

回答1:

Assuming the list is already data bound you can simply set the SelectedValue property on your dropdown list.

list.DataSource = GetListItems(); // <-- Get your data from somewhere.
list.DataValueField = "ValueProperty";
list.DataTextField = "TextProperty";
list.DataBind();

list.SelectedValue = myValue.ToString();

The value of the myValue variable would need to exist in the property specified within the DataValueField in your controls databinding.

UPDATE: If the value of myValue doesn't exist as a value with the dropdown list options it will default to select the first option in the dropdown list.

回答2:

ddlData.SelectedIndex will contain the int value To select the specific value into DropDown :

ddlData.SelectedIndex=ddlData.Items.IndexOf(ddlData.Items.FindByText("value"));

return type of ddlData.Items.IndexOf(ddlData.Items.FindByText("value")); is int.

回答3:

Here is the code I was looking for :

DDL.SelectedIndex = DDL.Items.IndexOf(DDL.Items.FindByText("PassedValue"));

Or

DDL.SelectedIndex = DDL.Items.IndexOf(DDL.Items.FindByValue("PassedValue"));

回答4:

Well if I understood correctly your question. The Solution for setting the value for a given dropdownlist will be:

dropdownlist1.Text="Your Value";

This will work only if the value is existing in the data-source of the dropdownlist.

回答5:

If you need to select your list item based on an expression:

foreach (ListItem listItem in list.Items)
{
    listItem.Selected = listItem.Value.Contains("some value");
}

回答6:

var index = ctx.Items.FirstOrDefault(item => Equals(item.Value, Settings.Default.Format_Encoding));
ctx.SelectedIndex = ctx.Items.IndexOf(index);

OR

foreach (var listItem in ctx.Items)
  listItem.Selected = Equals(listItem.Value as Encoding, Settings.Default.Format_Encoding);

Should work.. especially when using extended RAD controls in which FindByText/Value doesn't even exist!

回答7:

ddList.Items.FindByText("oldValue").Selected = false;
ddList.Items.FindByText("newValue").Selected = true;

回答8:

On load of My Windows Form the comboBox will display the ClassName column of my DataTable as it's the DisplayMember also has its ValueMember (not visible to user) with it.

private void Form1_Load(object sender, EventArgs e)
            {
                this.comboBoxSubjectCName.DataSource = this.Student.TableClass;
                this.comboBoxSubjectCName.DisplayMember = TableColumn.ClassName;//Column name that will be the DisplayMember
                this.comboBoxSubjectCName.ValueMember = TableColumn.ClassID;//Column name that will be the ValueMember
            }

回答9:

Safety check to only select if an item is matched.

//try to find item in list.  
ListItem oItem = DDL.Items.FindByValue("PassedValue"));
//if exists, select it.
if (oItem != null) oItem.Selected = true;

回答10:

            ddlemployee.DataSource = ds.Tables[0];
            ddlemployee.DataTextField = "Employee Name";
            ddlemployee.DataValueField = "RecId";
            ddlemployee.DataBind();
            ddlemployee.Items.Insert(0, "All");