For this you can make use of Split function available. Below is a sample code.
For testing i have added one textbox where i can enter data, a button and two textbox where data will be populated. After hitting button, you can use below code to populate.
protected void Button1_Click(object sender, EventArgs e)
{
string text = TextBox1.Text;
string [] text2 = text.Split('#');
int i = 1;
foreach (string item in text2)
{
if (i==1)
{
TextBox2.Text = item;
}
else if(i==2)
{
TextBox3.Text = item;
}
i++;
}
}
Please mark as answer if it helps!!!