How to retrieve the data into TextBox from

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C#

Hello sir,
I had created the PatientFirstname(P_FNAME) with textbox,P_LName(lastname)with textbox,& P_MName(middlename)with textbox and also i had created the P_FNAME,P_MNAME,P_LNAME fields in the MSSQL.So what i need is-


1. If i enter the textbox of P_FName(FIRSTNAME) in the output window other P_MNAME& P_LNAME has to be automatically displayed in their textboxes.
OR

2. If i enter the textbox of P_MName(MIDDLENAME) in the output window other P_FNAME& P_LNAME has to be automatically displayed in their textboxes.

3. and viceversa for P_LNAME(lastname).

Here for all the fields(P_FNAME,P_MNAME,P_LNAME) i had already entered the name in there columns.So how to retrieve from MSSQL into there textboxs.
<b>Plz do help me in this regard.
</b>
Thanks,
Pradeep CBZ