How to pass the value from a selected row(gridview) into another?

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C#

I have a page with a gridview:
Person.aspx

ID||Name||Mail||Phone

the value of this gridview is saved in an SQL table named Person.

under the gridview there is a button(Add Task)
if you click on it, you will get to another page(Task.aspx) with 3 TextBoxes:
Title, Task, & Deadline; the value of this Textboxes is saved in an SQL table named Task.

The SQL Table Task has 4 columns Titel, Task, Deadline AND Name.

Soo long story short: I want that, if you choose a Person from the gridview an add a task the Name of the Person should be saved automatically into the SQL Table Task "Name"

What I have tried:

I think it should be SelectedIndexChanged Methode, but unfortunately, nothing comes to my mind