private void button2_Click(object sender, EventArgs e) { String libraryCardID = textBox1.Text; LibraryCard card = AS.HaveLibraryCard(libraryCardID); if (null == card) { MessageBox.Show("用户ID错误!"); return; } label6.Text = card._Name; string sql = "select damageRecord.damageIndex,damageReason.damageExplain,circuBookClass.bookName,damageRecord.damageTime,damageRecord.damageMoney " + "from damageRecord join(circuBook join circuBookClass on circuBook.isbn = circuBookClass.isbn)on damageRecord.circuBookNo = circuBook.circuBookNo " + "join damageReason on damageReason.damageReasonIndex = damageRecord.damageReasonIndex " + "where damageRecord.damageRtnTIme is NULL and damageRecord.libraryCardID = @libraryCardID"; SqlParameter para = new SqlParameter("@libraryCardID", libraryCardID); dataTable = SQLHelper.getDataTable(sql, para); dataGridView1.AutoGenerateColumns = false; dataGridView1.DataSource = dataTable; //dataTable. decimal amount = 0; if (dataTable.Rows.Count == 0) { MessageBox.Show("该用户无欠费记录"); return; } for (int i = 0; i < dataTable.Rows.Count; i++) { amount = amount + decimal.Parse(dataTable.Rows[i]["damageMoney"].ToString()); } textBox2.Text = amount.ToString(); button3.Enabled = true; }