how to add text from textbox with each value of string array in c#

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C#

MS-Excel

plugin

hello everyone. i am developing a excel plugin. i have a widow form which contains textbox, listbox ,datagridview and a button. in listbox i make a list of all column headers like A,B,C,etc. from excel. when i select 'A' from listbox ,it will select all the usedrange values of A from excel. now i want that when i select from listbox then it will select that column values and convert into string array or object (positively i do not what should it). this string array should be add with my text as i write in textbox and show in datagridview rows. thanks for any help in advance.
This example is what i want to do:

string[] str={ram,shyam,geeta}

textbox text + string array/object = datagridview rows

hello + ram = hello ram
+ shyam = hello shyam
+ geeta = hello geeta

please help me.