How to change value of a column in DataGridView?

Hiii,

In a C# WinApp, I have a form with a DataGridView and a ComboBox. the DataGridView contains columns i.e. No; Perticular, Quantity, Rate, Amount and Days. the ComboBox contains number 1 to 365.

Now, I am trying to change the 6th column (Days) using the ComboBox numbers. I want to do it as if I select '10' from the ComboBox all the cells in the Days column get that value. In short, I want to change the entire column value with the value selected from the ComboBox regardless, how many rows are there in the gridview.

 

Anybody please help.

 

Thank You.

 

Mayank Jani.