how to generate text from SQL in textbox in ASP.NET

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ASP.NET

I have a SQL Table named PROFILE in which there are three columns (ID , UserName ,Email) ... ID is autogenerated and is a PRIMARY KEY , heres some dummy data for that table .
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ID | UserName | Email
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1 Raheel abc@gmail.com
2 Kamaal xyz@gmail.com
3 Jamaal ksd@gmail.com
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Also i have a asp.net web form in which i have a TEXTBOX (whose ID is ValueBox) , what i want is that when a user types e.g (PROFILE.UserName) withour brackets and then press spacebar the UserName appears and replace that PROFILE.UserName written in that TextBox .... for e.g if i am talking about ID 1 , which is Raheel ... when a user types " My name is Profile.UserName" and after Profile.UserName he press Spacebar the text in TextBox becomes " My name is Raheel" ... how to do this in asp.net C# ... ??