Regular expression to avoid special characters

private bool IsValidName(string strtxt)
{
bool returnValue = false;
Regex regx = new Regex(@"^[\w\s -]*$");
returnValue = regx.IsMatch(strtxt);
return returnValue;
}
protected void Button1_Click(object sender, EventArgs e)
{
if (!IsValidName(txtA.Text))
{
Response.Write("Entered Special Charectors-Not correct name");
}
else
{
Response.Write(txtA.Text);
}
}