Replacing a certain text in the textbox in asp.net

Hi guyzz,
My issue is that i need to replace certain text in my textbox with some other string.
Eg:- my name is abc. this name means something.
Now, i need to replace 'name' with 'hobby'.
this can be done using  
TextBox1.Text=TextBox1.Text.Replace("name","hobby");
This statement replaces every occurence of name in the textbox.
How can I just replace any one of the occurence of the string from multiple occurences(using asp.net c#).