ASP.NET C＃中的Gridview

Question

我有兩個下拉列表，對應於值，應該顯示gridview，下面是它的代碼。.但是我沒有得到問題所在！

protected void ddlstudents_SelectedIndexChanged(object sender, EventArgs e)
{
    if (ddlstudents.SelectedIndex > 0)
    {
        BindData();
    }
}

private void BindData()
{
    try
    {
        SQLiteConnection con = new SQLiteConnection("data source=C:\\ITS Database\\its.development.sqlite3");

        string strquery = "select topics.name,course_coverages.progress from topics JOIN course_coverages on topics.id=course_coverages.topic_id where course_coverages.student_id=@studentid AND course_coverages.course_id=@courseid";

        con.Open();
        SQLiteCommand cmd = new SQLiteCommand();
        cmd.connection=con;
        cmd = con.CreateCommand();
        cmd.CommandText = strquery;

        cmd.Parameters.AddWithValue("@studentid", ddlstudents.SelectedIndex);
        cmd.Parameters.AddWithValue("@courseid", ddlcourse.SelectedValue);

        SQLiteDataAdapter ada = new SQLiteDataAdapter(cmd.CommandText, con);

        SQLiteCommandBuilder cbl = new SQLiteCommandBuilder(ada);
        DataTable dt = new DataTable();
        ada.Fill(dt);
        GridView1.DataSource = dt;
        GridView1.DataBind();
        con.Close();
    }

    catch (SQLiteException)
    {

    }
}

任何幫助，將不勝感激！！

提前致謝！！

Answer 1

了解如何找到自己的問題。 如果gridview沒有顯示正確的數據，則可以調試應用程序並查找失敗的地方。

您尚未給出如何綁定ddlstudents和ddlcourse ，請檢查是否為ddlstudents.SelectedIndex和ddlcourse.SelectedValue獲得的值是否ddlcourse.SelectedValue您的預期。

如果值正確，則可以使用上述值在數據庫上運行SQL語句並查看結果。

如果您確實需要查找錯誤，請從代碼中刪除try catch語句，

如果發現異常，請對其進行處理。 否則不要。

Answer 2

嘗試這個

protected void ddlstudents_SelectedIndexChanged(object sender, EventArgs e)
{
    if (ddlstudents.SelectedIndex > 0)
    {
        BindData();
    }
}

private void BindData()
{
    try
    {
        SQLiteConnection con = new SQLiteConnection("data source=C:\\ITS Database\\its.development.sqlite3");

        string strquery = "select topics.name,course_coverages.progress from topics JOIN course_coverages on topics.id=course_coverages.topic_id where course_coverages.student_id=@studentid AND course_coverages.course_id=@courseid";

        con.Open();
        SQLiteCommand cmd = new SQLiteCommand();
        cmd.connection=con;
        cmd = con.CreateCommand();
        cmd.CommandText = strquery;

        cmd.Parameters.AddWithValue("@studentid", ddlstudents.SelectedValue);
        cmd.Parameters.AddWithValue("@courseid", ddlcourse.SelectedValue);

        SQLiteDataAdapter ada = new SQLiteDataAdapter(cmd.CommandText, con);

        SQLiteCommandBuilder cbl = new SQLiteCommandBuilder(ada);
        DataTable dt = new DataTable();
        ada.Fill(dt);
        GridView1.DataSource = dt;
        GridView1.DataBind();
        con.Close();
    }

    catch (SQLiteException)
    {

    }
}