Question

I have an editable ComboBox with a validation on the Text property to make sure manually entered info is valid.

EDIT: All I want to do is populate the .Text property with the ValueMember of a selection rather than the DisplayMember

I also have the .Items populated with valid entries having the DisplayMember and ValueMember set.

My DisplayMember is a caption along with the data, and the ValueMember is the data itself.

So Items might be:

(DisplayMember, ValueMember)
"Foo - 1ab2"  , "1ab2"
"Bar - 3cd4"  , "3cd4"

I had a validation on the text which can also validate manual user input like “5ef6”

The problem I’m having is that if the user selects an item from the combobox it populates the text field with the DisplayMember property (ex: “Foo – 1ab2”) which will fail validation.

I have tried to manually set the .Text property with the SelectedValue or the SelectedItem.Value on each of the three relevant combobox events to no avail.

I would like that the .Text of the ComboBox get populated with the .ValueMember of the item when selected rather than the .DisplayMember

EDIT: I cannot validate by trying to extrapolate the value from the caption. I send the Text off to a service to be validated.

void FillMyCombo
{
    KeyValuePair<string, string> listValue1 = new KeyValuePair<string, string>("Foo - 1ab2"  , "1ab2")
    KeyValuePair<string, string> listValue2 = new KeyValuePair<string, string>("Bar - 3cd4"  , "3cd4")
    myCombo.Items.Add(listValue1);
    myCombo.Items.Add(listValue2);

    myCombo.DisplayMember = "Key";
    myCombo.ValueMember = "Value";
}

...

void myCombo_TextUpdated
{
    if(!myValidationService.Validate(myCombo.Text))
    {
        do error stuff
    }
}

The user can manually enter something like “5ef6” which will pass validation.
But when they select an item from the list, rather than manually entering it, the .Text property gets filled with the caption and not the value … so it will contain “Foo – 1ab2” and that will fail validation.

EDIT: In response to an answer posted: I cannot change the validation method to “infer” the value from the caption. I have no control over that service. All I’m after is the displayed value

EDIT: Say a user selects “Foo – 1ab2” from the dropdown list, I want the text in the box to say “1ab2”

EDIT: I have also tried to set the .Text property in code but I can’t seem to make it work in any of the ComboBox events. If anybody can answer how to programmaticly set the .Text property (and make it commit!) on a selection event they will also answer this question.

Answer 1

What about http://nickstips.wordpress.com/2010/11/19/c-datagridviewcomboboxcolumn-displaying-different-values-in-drop-down-list/ — they change ValueMember and DisplayMember on the fly upon dropdown opening/closing.

Example is for DatagridViewComboBox. A ComboBox has those events, too, no?

Give it a try and downvote if it does not help :)=

** Update **

Another good-looking solution might be ArgumentException when adding ComboBox column to DataGridView with same DataSource, there look at the not-accepted answer.