将布尔参数传递给SQL Server存储过程

我之前问过这个问题，我以为我发现了问题所在，但我没有。将布尔参数传递给存储过程时遇到问题。这是我的c#代码：

public bool upload = false;
protected void showDate(object sender, EventArgs e)
{
        if (Radio1.Checked)
        {
            upload = true;
            Radio2.Checked = false;
            date_div.Visible = true;
            date_div2.Visible = false;
        }
}
protected void getMonthList()
{
    selectedYear = year.SelectedValue.ToString();
    SqlConnection connection = new SqlConnection(connString);
    SqlCommand cmd = connection.CreateCommand();
    cmd.CommandType = CommandType.StoredProcedure;
    connection.Open();
    cmd.CommandText = "getMonth";
    cmd.Parameters.Add("@year", SqlDbType.Int, 0).Value = Convert.ToInt32(selectedYear);
    cmd.Parameters.AddWithValue("@upload", upload);
    DataTable dt = new DataTable();
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    da.Fill(dt);
    month.DataSource = dt;
    month.DataTextField = "month";
    month.DataValueField = "monthValue";
    month.DataBind();
    month.Items.Insert(0, new ListItem("Select", "0"));
}

这就是存储过程getMonth:

ALTER PROCEDURE [dbo].[getMonth] 
    @year int,
    @upload Bit
AS
BEGIN
  IF @upload = 1
  BEGIN
   SELECT distinct datename(mm, Upload_date) month
    ,month (upload_date) monthValue
   FROM dbo.RESOLVED
   WHERE datepart(yyyy, upload_date) = @year
   ORDER by 2
  END
  ELSE
  BEGIN
    SELECT distinct datename(mm, substring(CREATE_DT,1,2) + '.' +      substring(CREATE_DT,3,2) + '.' + substring(CREATE_DT,5,4)) month
    ,month (substring(CREATE_DT,1,2) + '.' + substring(CREATE_DT,3,2) + '.' + substring(CREATE_DT,5,4)) monthValue
    FROM dbo.RESOLVED
    WHERE datepart(yyyy, substring(CREATE_DT,1,2) + '.' + substring(CREATE_DT,3,2) + '.' + substring(CREATE_DT,5,4)) = @year
    ORDER by 2
 END

存储过程应该填充dropdownlist。它应该执行IF语句，但跳过了IF，而是执行ELSE。

            SqlParameter param = new SqlParameter();
            param.ParameterName = "@upload";
            param.Value = upload;
            param.DbType = System.Data.DbType.Boolean
            cmd.Parameters.Add(param);