一個有關Update類型的預存程序的問題

CREATE PROCEDURE testupdateproc   AS
declare @id int
declare @trandate datetime
declare @tranlimit int
update test set trandate=@trandate, tranlimit=@tranlimit where test.id=@id
GO
預存程序語句如上，檢查文法是沒有問題的，但是在程式中執行時卻不行。程式如下：
            Class1 c= new Class1();
            System.Data.SqlClient.SqlParameter[] para = new System.Data.SqlClient.SqlParameter[3];
            para[0] = new System.Data.SqlClient.SqlParameter("@id",this.textBox3.Text);
             if (this.textBox1.Text != "")
                para[1] = new System.Data.SqlClient.SqlParameter("@trandate", this.textBox1.Text);
            else
                para[1] = new System.Data.SqlClient.SqlParameter("@trandate", DBNull.Value);
            if (this.textBox2.Text != "")
                para[2] = new System.Data.SqlClient.SqlParameter("@tranlimit", this.textBox2.Text);
            else
                para[2] = new System.Data.SqlClient.SqlParameter("@tranlimit", DBNull.Value);
            //c.DataInsert();
            if (c.DataUpdate())
                MessageBox.Show("OK");
            else
                MessageBox.Show("False");
DataUpdae方法如下：
         public bool DataUpdate()
        {
            string strConn = "Server=.;Initial Catalog=test;User Id=sa;Password=123";
            SqlConnection sqlcon = new SqlConnection(strConn);
            sqlcon.Open();
            SqlCommand sqlcom = new SqlCommand();
            sqlcom.Connection = sqlcon;
            sqlcom.CommandType = CommandType.StoredProcedure;
            sqlcom.CommandText = "testupdateproc";
            int i = sqlcom.ExecuteNonQuery();
            sqlcon.Close();
            bool flag = false;
            if (i > 0)
                flag = true;
            else
                flag = false;
            return flag;
        }
程式執行返回的是false ，資料庫中資料也沒有改變，大家看看是怎麼回事？