code crashing

Hi,
Iam written the code for creating a textboxs dynamically in asp.net. but its working fine for single user, when multi users are using that code it become crashing so i want to give unique for that code but its not a secure page
My Code:

if (!IsPostBack)
{
for (int a = 0; a < txt_arrSkills.Length; a++)
{
txt_arrSkills[a] = null;
}
}

if (txt_arrSkills[0] is TextBox)
{
foreach (TextBox firstTxtBox in txt_arrSkills)
{
addFirstTxtBox(firstTxtBox);

}
}

protected void addFirstTxtBox(TextBox firstTxtBox)
{
try
{
TableRow tr = new TableRow();
TableCell tc = new TableCell();
tc.Controls.Add(firstTxtBox);
tr.Cells.Add(tc);
tblSkills.Rows.Add(tr);
}
catch (Exception)
{
}
}

protected void ldynControls_Click(object sender, EventArgs e)
{
new_txtSkills = new TextBox();
int skillValue = 20;
for (int a = ...