How to set deafault value in combobox

A better approach is to fetch Id from your datasource and then assign it to dropdown selected value .

If you have Datasource type Table then you can do something like this.

combobox1.SelectedValue= table.Select("tt='USD'")[0]["Id"];

Assuming "USD" would always be in datasource. If not this code would throw exception. Then in that case you may apply

DataRow[] rows = table.Select("tt='USD'");

if(rows.Length>0)
 combobox1.SelectedValue=  rows[0]["Id"];

Hope this would be helpful.

comboBox1.SelectedItem = "USD";

Also works.

fyi: 'SelectedItem' is a native property of the ComboBox control: 'SelectedValue' is an inherited property from ListControl. In practice this makes little difference except perhaps in scnearios where you are using databinding. See:[^]

But, note that SelectedItem works by: "The ComboBox class searches for the specified object by using the IndexOf method. This method uses the Equals method to determine equality." ... from the .C# docs.

If you are setting/re-setting the default Currency frequently in your application, or perhaps the list of currencies changes dynamically, probably better to calculate, when you need to, the default currency's index in the ComboBox List, stick that in an integer variable, and then use that variable as the argument to SelectedIndex.

But, if this is a one off, done at application initialization, and the default currency list is not changed, or does not need to be 'reset,' it probably doesn't matter which technique you use.

combobox1.SelectedValue= "INR";