Asp.Net 判斷TEXTBox輸入字節長度

public int CountByte(String strToByte, Encoding enc)
{

return enc.GetByteCount(strToByte);
}

protected void btnSave_Click(object sender, EventArgs e)
{
//以下為中文為2個字節，英文為一個字節

if(CountByte(txtProjectName.Text,Encoding.UTF8)>50)
{
RFQCommon.ShowMsg(this, "Project Name can not over 50 Charater.");
return;
}

//如編碼方式更改為Encoding.Unicode中文及英文均為2個字節

if(CountByte(txtProjectName.Text,Encoding.Unicode)>50)
{
RFQCommon.ShowMsg(this, "Project Name can not over 50 Charater.");
return;
}

}