If i understand your problem correctly, you want to get the text of the selected item, when a selection changes (?)
I recommend you use the selectedindexchanged event, there is a selectedvaluechange event, but it is for unknown reasons not as reliable.
Here you can use the very nice index (most reliable) in the list to access the individual data
https://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.selectedindexchanged(v=vs.110).aspx[
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and if you want to access the text of the selected text, it much depends on what you're binding on, as the implementation states that it is an object it could be anything
https://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.selectedindex(v=vs.110).aspx[
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However a Combobox is a listcontrol and as such it supports two properties "displaymember" and "valuemember", it is the displaymember property you want to if the value "displaymember" is not supplied it will have a value "" and in this case cause a call to the .ToString() method of the object.
So supply the displaymember to your combobox and then cast the item the type you're binding to and access the (property) named like that, this should be dotable after casting.