ExecuteReader：CommandText屬性未初始化

Question

public DataTable Liste()
{
    SqlConnection con = new SqlConnection("Data Source=DESKTOP-JHLF03K\\SQLEXPRESS;Initial Catalog=OtelWebSite;Integrated Security=True");
    string sql = "";
    SqlDataAdapter dap = new SqlDataAdapter(sql, con);  
    DataTable table = new DataTable();
    con.Open();
    dap.Fill(table);

    sql += "SELECT ";
    sql += "O.Id, ";
    sql += "O.OdaTurId,";
    sql += "T.Ad AS OdaTur, ";
    sql += "O.Ad, ";
    sql += "O.KatNo, ";
    sql += "O.Aciklama, ";
    sql += "K.Tanim AS Durum ";
    sql += "FROM Oda O, Kod K,OdaTur T  ";
    sql += "WHERE O.Durum = K.Kod ";
    sql += "AND T.Id = O.OdaTurId ";
    sql += "ORDER BY O.Id,O.OdaTurId";



    con.Close();
    return table;
}

我得到一個錯誤

ExecuteReader：CommandText屬性未初始化

在這行代碼上：

dap.Fill(table);

Answer 1

您無法執行並清空sql查詢。 將您的sql查詢創建移動到創建DataAdapter的行之前的頂部

public DataTable Liste()
{
    SqlConnection con = new SqlConnection("Data Source=DESKTOP-JHLF03K\\SQLEXPRESS;Initial Catalog=OtelWebSite;Integrated Security=True");
    string sql = "";

    sql += "SELECT ";
    sql += "O.Id, ";
    sql += "O.OdaTurId,";
    sql += "T.Ad AS OdaTur, ";
    sql += "O.Ad, ";
    sql += "O.KatNo, ";
    sql += "O.Aciklama, ";
    sql += "K.Tanim AS Durum ";
    sql += "FROM Oda O, Kod K,OdaTur T  ";
    sql += "WHERE O.Durum = K.Kod ";
    sql += "AND T.Id = O.OdaTurId ";
    sql += "ORDER BY O.Id,O.OdaTurId";

    SqlDataAdapter dap = new SqlDataAdapter(sql, con);  
    DataTable table = new DataTable();
    con.Open();
    dap.Fill(table);

    con.Close();
    return table;
}