如何获取数据集值

Question

VB.Net 新手，

如何插入或选择数据集值。

    cmd = New SqlCommand("Select * from table1", con)
    ada = New SqlDataAdapter(cmd)
    ds = New DataSet
    ada.Fill(ds)
    cmd = New SqlCommand("Select * from  '" & ds.Tables(0) & "'  ", con)
    mydatatable1.Load(dr3)

在'" & ds.Tables(0) & "'显示错误，我要获取数据集值

需要 VB.Net 代码帮助

Answer 1

在您尝试创建第二个 SqlCommand 之前，您有一个合理的想法。也就是说，一旦你完成了填充，你就已经在表格中拥有了数据。你不会运行另一个选择 - 你已经这样做了。您只需引用要在数据集中使用的表。

如果你想要一个数据表，你可以这样做（对于 VB，见下文）：

    SqlDataAdapter myAdapter = new SqlDataAdapter(CommandText, con);
    DataSet myDataset = new DataSet();
    myAdapter.Fill(myDataset, "Table");  // "Table" is just a name, it can be anything.
    mydatatable1 = myDataset.Tables[0];  // Get the table

现在，如果您本身不需要 DataTable，而只想从查询中读取数据，则可以使用 SqlDataReader：

 cmd = new SqlCommand(CommandText, con);
 // One or more params
 cmd.Parameters.AddWithValue("@paramName", Value);
 SqlDataReader nwReader = cmd.ExecuteReader();

然后从 nwReader 中读取：

 while (nwReader.Read())
 {
     string field1Val = (string)nwReader["FieldName"];
     etc...
 }

---

更新：我不了解 VB，但这是我认为的样子：

cmd = New SqlCommand("Select * from table1", con) 
ada = New SqlDataAdapter(cmd) 
ds = New DataSet 
ada.Fill(ds) 
mydatatable1 = ds.Tables(0);

您可能可以缩短它以摆脱额外的 SqlCommand（假设 VB 支持这种 SqlDataAdapater 语法，如 C#。

ada = New SqlDataAdapter("Select * from table1", con) 
ds = New DataSet 
ada.Fill(ds) 
mydatatable1 = ds.Tables(0);

祝你好运……

Answer 2

您可以使用 Microsoft Enterprise Library 来简化此过程。这个库是处理数据集的强大库。

Answer 3

   public async Task<ResponseStatusViewModel> GetAll()
        {
            var responseStatusViewModel = new ResponseStatusViewModel();
            var connection = new SqlConnection(EmployeeConfig.EmployeeConnectionString);
            var command = new SqlCommand("usp_GetAllEmployee", connection);
            command.CommandType = CommandType.StoredProcedure;

            try
            {
                await connection.OpenAsync();
                var reader = await command.ExecuteReaderAsync();

                var dataSet = new DataSet();
                dataSet.Load(reader, LoadOption.OverwriteChanges, new string[] { "Employee" });
                reader.Close();
                reader.Dispose();

                var employees = new List<EmployeeModel>();

                if (dataSet.Tables.Count > 0 && dataSet.Tables["Employee"] != null)
                {
                    var employeeTable = dataSet.Tables["Employee"];

                    for (int i = 0; i < employeeTable.Rows.Count; i++)
                    {
                        var employeeRow = employeeTable.Rows[i];

                        employees.Add(new EmployeeModel
                        {
                            EmployeeID = Convert.ToInt32(employeeRow["EmployeeID"]),
                            EmployeeName = Convert.ToString(employeeRow["EmployeeName"]),
                            Address = Convert.ToString(employeeRow["Address"]),
                            GrossSalary = Convert.ToDouble(employeeRow["GrossSalary"]),
                            PF = Convert.ToDouble(employeeRow["PF"]),
                            TotalSalary = Convert.ToDouble(employeeRow["TotalSalary"])
                        });
                    }
                }
                responseStatusViewModel.Data = employees;
                command.Dispose();
                connection.Dispose();

            }
            catch (Exception ex)
            {

                throw ex;
            }

            return responseStatusViewModel;
        }

Answer 4

我认为你正在寻找的是

cmd = New SqlCommand("Select * from '" & ds.Tables(0).TableName & "'", con)

cmd = New SqlCommand("Select * from table1", con)
ada = New SqlDataAdapter(cmd)
ds = New DataSet
ada.Fill(ds)
cmd = New SqlCommand("Select * from  '" & ds.Tables(0).TableName & "'  ", con)
mydatatable1.Load(dr3)