如何用 SQL 表填充 DataTable

Question

我目前正在我的 Page_Load 中使用以下代码创建和读取 DataTable

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["AllFeatures1"] == null)
    {
        Session["AllFeatures1"] = GetData();
    }
    table = (DataTable)Session["AllFeatures1"];
    DayPilotCalendar1.DataSource = Session["AllFeatures1"];
    DayPilotNavigator1.DataSource = Session["AllFeatures1"];

    if (!IsPostBack)
    {
        DataBind();
        DayPilotCalendar1.UpdateWithMessage("Welcome!");
    }

    if (User.Identity.Name != "")
    {
        Panel1.Visible = true;
    }
}

我想知道如何转换此代码以便从 SQL 查询中读取？我正在试验下面的代码，但我不确定如何连接它们，以便我的页面加载中的数据表填充下面的 SQL 命令。

SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
conn.Open();
string query = "SELECT * FROM [EventOne]";

SqlCommand cmd = new SqlCommand(query, conn);

DataTable t1 = new DataTable();
using (SqlDataAdapter a = new SqlDataAdapter(cmd))
{
    a.Fill(t1);
}

我被困在：

table = (DataTable)Session["AllFeatures1"]; 

我希望它是t1 = (DataTable)Session["AllFeatures1];

Answer 1

SqlDataReader 是DataTable 的有效数据源。因此，您只需要这样做：

public DataTable GetData()
{
    SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
    conn.Open();
    string query = "SELECT * FROM [EventOne]";
    SqlCommand cmd = new SqlCommand(query, conn);

    DataTable dt = new DataTable();
    dt.Load(cmd.ExecuteReader());
    conn.Close();
    return dt;
}

Answer 2

您可以创建返回给定sql查询数据表的方法：

public DataTable GetDataTable()
{
SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
conn.Open();
string query = "SELECT * FROM [EventOne] ";

SqlCommand cmd = new SqlCommand(query, conn);

DataTable t1 = new DataTable();
using (SqlDataAdapter a = new SqlDataAdapter(cmd))
{
    a.Fill(t1);
}
return t1;
}

现在可以这样使用：

table = GetDataTable();

Answer 3

您需要修改方法GetData() 并在那里添加您的“实验”代码，并返回t1。

Answer 4

上面的答案是正确的，但我想如果您需要将参数传递到查询中，我会通过提供一种方法来扩展另一个答案。

SqlDataAdapter 快速而简单，但仅当您使用静态请求填充表格时才有效，即：简单的 SELECT 不带参数。

这是我的方法，但使用参数来控制我在表中需要的数据。我用它来填充DropDownList。

//populate the Programs dropdownlist according to the student's study year / preference
DropDownList ddlPrograms = (DropDownList)DetailsView1.FindControl("ddlPrograms");
if (ddlPrograms != null)
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ATCNTV1ConnectionString"].ConnectionString))
    {
        try
        {
            con.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "SELECT ProgramID, ProgramName FROM tblPrograms WHERE ProgramCatID > 0 AND ProgramStatusID = (CASE WHEN @StudyYearID = 'VPR' THEN 10 ELSE 7 END) AND ProgramID NOT IN (23,112,113) ORDER BY ProgramName";
            cmd.Parameters.Add("@StudyYearID", SqlDbType.Char).Value = "11";
            DataTable wsPrograms = new DataTable();
            wsPrograms.Load(cmd.ExecuteReader());

            //populate the Programs ddl list
            ddlPrograms.DataSource = wsPrograms;
            ddlPrograms.DataTextField = "ProgramName";
            ddlPrograms.DataValueField = "ProgramID";
            ddlPrograms.DataBind();
            ddlPrograms.Items.Insert(0, new ListItem("<Select Program>", "0"));
        }
        catch (Exception ex)
        {
            // Handle the error
        }
    }
}

享受

Answer 5

您可以像下面的代码一样填写您的数据表。我还在运行时使用具有所有连接的预定义 XML 文件来获取连接。

  public static DataTable Execute_Query(string connection, string query)
    {
        Logger.Info("Execute Query has been called for connection " + connection);
        connection = "Data Source=" + Connections.run_singlevalue(connection, "server") + ";Initial Catalog=" + Connections.run_singlevalue(connection, "database") + ";User ID=" + Connections.run_singlevalue(connection, "username") + ";Password=" + Connections.run_singlevalue(connection, "password") + ";Connection Timeout=30;";
        DataTable dt = new DataTable();
        try
        {
            using (SqlConnection con = new SqlConnection(connection))
            {
                using (SqlCommand cmd = new SqlCommand(query, con))
                {
                    con.Open();
                    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                    {
                        da.SelectCommand.CommandTimeout = 1800;
                        da.Fill(dt);
                    }
                    con.Close();
                }
            }
            Logger.Info("Execute Query success");
            return dt;
        }
        catch (Exception ex)
        {
            Console.Write(ex.Message);
            return null;
        }
    }