C# 使用组合框选择来预填充文本框的

Question

我是一个非常菜鸟的程序员，正在尝试编写一小部分软件。

在这段代码中，我尝试在新选择 ComboBox 时以包含来自 OleDB 数据库的详细信息的形式预填充文本框。

基本上，单击 ComboBox 中的名称会预先填充一些文本框，其中包含有关该名称的详细信息。

问题是代码没有将数据中的值赋给文本框。取而代之的是文本框的显示“0”。

我该如何解决这个问题？

private void cbbEmployees_SelectedIndexChanged(object sender, EventArgs e)
    {
        int PayrollNo = 0;
        int AnnualHolidayEntitlemet = 0;
        int DaysTakenToDate = 0;

        string Query = "SELECT PayrollNo, AnnualHolidayEntitlement, DaysTakenToDate FROM [Employee] WHERE FirstName +  ' ' + LastName = ?";
        string ConnString = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\HoliPlanData.accdb;Persist Security Info=False";

        using (OleDbConnection conn = new OleDbConnection(ConnString))
        using (OleDbCommand GetAllcmd = new OleDbCommand(Query, conn))
        {

            conn.Open();
            GetAllcmd.Parameters.Add("?", OleDbType.VarChar).Value = cbbEmployees.Text;
            GetAllcmd.Parameters.Add("@PayrollNo", OleDbType.VarChar).Value = PayrollNo;               
            GetAllcmd.Parameters.Add("@AnnualHolidayEntitlement", OleDbType.VarChar).Value = AnnualHolidayEntitlemet;
            GetAllcmd.Parameters.Add("@DaysTakenToDate", OleDbType.VarChar).Value = DaysTakenToDate;
            GetAllcmd.ExecuteScalar();


            txtPayrollNo.Text = PayrollNo.ToString();
            txtAHE.Text = AnnualHolidayEntitlemet.ToString();
            txtDTTD.Text = DaysTakenToDate.ToString();
            txtDaysRemaining.Text = (AnnualHolidayEntitlemet - DaysTakenToDate).ToString();
        }
    }

Answer 1

private void cbbEmployees_SelectedIndexChanged(object sender, EventArgs e)
    {
        int PayrollNo = 0;
        int AnnualHolidayEntitlemet = 0;
        int DaysTakenToDate = 0;

        string Query = "SELECT TOP(1) PayrollNo, AnnualHolidayEntitlement, DaysTakenToDate FROM [Employee] WHERE FirstName" +  "' '" + "LastName = @param";
        string ConnString = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\HoliPlanData.accdb;Persist Security Info=False";

        using (OleDbConnection conn = new OleDbConnection(ConnString))
        using (OleDbCommand GetAllcmd = new OleDbCommand(Query, conn))
        {

            conn.Open();
            GetAllcmd.Parameters.AddWithValue("@param", cbbEmployees.Text);


            //GetAllcmd.ExecuteScalar(); use GetAllcmd.ExecuteReader() instead
            OleDbDataReader oleDR;
                    oleDR = GetAllcmd.ExecuteReader();
                    if (oleDR.HasRows)
                    {
                         txtPayrollNo.Text = oleDR["PayrollNo"].ToString();
                         txtAHE.Text = oleDR["AnnualHolidayEntitlemet"].ToString();
                         txtDTTD.Text = oleDR["DaysTakenToDate"].ToString();
                         txtDaysRemaining.Text = (oleDR["AnnualHolidayEntitlemet"] - oleDR["DaysTakenToDate"]).ToString();

                    }


        }
    }

Answer 2

https://whosebug.com/users/5292801/takarii

感谢 takarii 的广泛指导 ^^.. 以下是该问题的有效解决方案！

    private void cbbEmployees_SelectionChangeCommitted(object sender, EventArgs e)
    {
        string Query = "SELECT PayrollNo, AnnualHolidayEntitlement, DaysTakenToDate FROM [Employee] WHERE PayrollNo =" + Convert.ToInt32(cbbEmployees.SelectedValue); 


        string ConnString = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\HoliPlanData.accdb;Persist Security Info=False";

        using (OleDbConnection conn = new OleDbConnection(ConnString))
        using (OleDbCommand GetAllcmd = new OleDbCommand(Query, conn))
        {
            DataTable dt = new DataTable();
            conn.Open();
            dt.Load(GetAllcmd.ExecuteReader());
            conn.Close();

             txtPayrollNo.Text = dt.Rows[0][0].ToString();
             txtAHE.Text = dt.Rows[0][1].ToString();
             txtDTTD.Text = dt.Rows[0][2].ToString();


        }
    }

Answer 3

我的代码示例使用第一个找到的记录的数据。

您可以使用 select Top 1 ....调整您的查询。确保您有正确的记录。

如果您的结果集可能包含多个记录，您需要稍后处理 (oleDR.Read()) { // 做一点事 }

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