[英]C# best way to handle SQL query
我想用一個函數讀取數據庫記錄,並將結果作為數組傳遞給另一個函數。 如何使用.NET4.5?
namespace test
{
class Program
{
static void Main()
{
... data = GetData();
string result = HandleData(data);
}
private static string HandleData(... data)
{
return string result
}
private static ... GetData()
{
... result = new ...;
SqlDataReader reader;
using (SqlConnection conn = new SqlConnection(conf))
{
string query = "SELECT [ID], [Desc], [tID] FROM [table] WHERE [Updated] = 0";
try
{
conn.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = query;
cmd.Connection = conn;
reader = cmd.ExecuteReader();
if(reader.HasRows)
{
while (reader.Read())
{
result.Add(reader[0], reader[1], reader[2]);
}
}
reader.Close();
}
catch(Exception e)
{
}
finnaly
{
conn.Close();
conn.Dispose();
}
}
return result;
}
}
}
我應該將Wich數據類型用於result
變量,以及如何更正內部的組織數據?
遵循stackoverflow的規則,我將此文本添加到我的問題中,因為它說該問題主要包含代碼。
您可以將值從sql存儲到datatable,然后可以通過使用linq將datatable轉換為arrey,這是代碼
Private static ... GetData()
{
try
{
var dt = new DataTable();
var cmd = new SqlCommand();
cmd.CommandText = @"SELECT name,address FROM [table_name] WHERE id = @id";
cmd.Parameters.AddwithValue("@id",id);
var da = new SqlDataAdapter(cmd);
da.Fill(dt);
}
catch (Exception ex)
{
}
finally
{
if (cmd.Connection.State == ConnectionState.Open)
{
cmd.Connection.Close();
}
}
var stringArr = dt.Rows[0].ItemArray.Select(x => x.ToString()).ToArray();
return stringArr;
}
我認為最好的解決方案是:
private static DataTable GetData()
{
DataTable result = new DataTable();
using (SqlConnection conn = new SqlConnection(conf))
{
string query = "SELECT [ID], [Desc], [tID] FROM [table] WHERE [Updated] = 0";
try
{
conn.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = query;
cmd.Connection = conn;
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(result);
da.Dispose();
}
catch(Exception e)
{
}
finnaly
{
conn.Close();
conn.Dispose();
}
}
return result;
}
您應該構造DTO(數據傳輸對象)以在應用程序周圍傳遞值。
private static void Main(string[] args)
{
var dt = new DataTable();
var col = new DataColumn { DataType = typeof(int), ColumnName = "ID" }; dt.Columns.Add(col);
col = new DataColumn { DataType = typeof(string), ColumnName = "Desc" }; dt.Columns.Add(col);
col = new DataColumn { DataType = typeof(int), ColumnName = "tID" }; dt.Columns.Add(col);
var row = dt.NewRow();
{
row["ID"] = 1;
row["Desc"] = "This is description";
row["tID"] = 2;
}
dt.Rows.Add(row);
var dto = ToDTO<UpdatedDto>(dt);
}
private static List<object> ToDTO<T>(DataTable dt)
{
var reult = (from rw in dt.AsEnumerable()
select new UpdatedDto
{
ID = Convert.ToInt32(rw["ID"]),
Desc = Convert.ToString(rw["Desc"]),
tID = Convert.ToInt32(rw["tID"])
}).ToList();
return reult.ConvertAll<object>(o => (object)o);
}
這是我如何提取數據並將其解析為數組的方法代碼段。
public int find_data_on_id(string id, out string[] strTxnid)
{
cmd.Parameters.Clear();
cmd.CommandText = @"SELECT name,address FROM [table_name] WHERE id = @id";
cmd.Parameters.AddwithValue("@id",id);
strTxnid = new string[5];
try
{
SqlDataReader dr = cmd.ExecuteReader();
dr.Read();
strTxnid[0] = dr["id"].ToString();
strTxnid[1] = dr["name"].ToString();
strTxnid[2] = dr["address"].ToString();
dr.Close();
return 0;
}
catch (Exception ex)
{
console.writeline("db internal error");
return -1;
}
}
通話范例:
public void example_call()
{
string[] info;
int Respond = find_data_on_id(1,out info );
string name = info[1];
string address = info[2];
}
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