Question

我在jquery中有15个ajax调用，它同时执行，调用它们各自的c＃函数（每个ajax都有单独的c＃函数）以下是样本c＃sql函数

public static DataSet Function1(int arg, string arg2, string arg3, string arg4, int arg5, int arg6)
        {

            DataSet ds = new DataSet();

            try
            {

                using (SqlConnection con = DbHelper.Connect())
                {
                    con.Open();
                    using (SqlCommand cmd = con.CreateCommand())
                    {
                        cmd.CommandText = "Procedure_Name";
                        cmd.CommandType = CommandType.StoredProcedure;
                        cmd.Parameters.AddWithValue("@arg", arg);
                        cmd.Parameters.AddWithValue("@arg1", arg1);

                        cmd.Parameters.AddWithValue("@arg2", arg2);
                        cmd.Parameters.AddWithValue("@arg3", arg3);
                        cmd.Parameters.AddWithValue("@arg4", arg4);
                        // cmd.Parameters.AddWithValue("@arg5", arg5);
                        cmd.CommandTimeout = 0;
                        var dataAdaptor = new SqlDataAdapter(cmd);
                        dataAdaptor.Fill(ds);
                    }
                    con.Close();
                }

                ds.Tables[0].TableName = "Test";



            }
            catch (Exception ex)
            {

                throw ex;

            }

            return ds;
        }

我偶尔会遇到异常

 Message:Object reference not set to an instance of an object.
Source:System.Data
Target site:Boolean TryOpenInner(System.Threading.Tasks.TaskCompletionSource1[System.Data.ProviderBase.DbConnectionInternal])
Stack Trace:   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1 retry)
   at System.Data.SqlClient.SqlConnection.Open()

任何帮助将不胜感激

  using System;
using System.Data;
using System.Data.Common;
using System.Configuration;
using System.Data.SqlClient;

{
    public class DbHelper : IDisposable
    {


        public static string _connString = ConfigurationManager.AppSettings["ConfigurationString"];
        protected static SqlConnection _conn = null;
        protected SqlTransaction _trans = null;
        protected bool _disposed = false;

        /// <summary>
        /// Sets or returns the connection string use by all instances of this class.
        /// </summary>
        /// 

        public static string ConnectionString { get; set; }

        /// <summary>
        /// Returns the current SqlTransaction object or null if no transaction
        /// is in effect.
        /// </summary>
        public SqlTransaction Transaction { get { return _trans; } }

        /// <summary>
        /// Constructor using global connection string.
        /// </summary>
        public DbHelper()
        {
            _connString = ConnectionString;
            Connect();
        }

        /// <summary>
        /// Constructure using connection string override
        /// </summary>
        /// <param name="connString">Connection string for this instance</param>
        public DbHelper(string connString)
        {
            _connString = connString;
            Connect();
        }

        // Creates a SqlConnection using the current connection string
        public static SqlConnection Connect()
        {
            _conn = new SqlConnection(_connString);           
            return _conn;
        }

        /// <summary>
        /// Constructs a SqlCommand with the given parameters. This method is normally called
        /// from the other methods and not called directly. But here it is if you need access
        /// to it.
        /// </summary>
        /// <param name="qry">SQL query or stored procedure name</param>
        /// <param name="type">Type of SQL command</param>
        /// <param name="args">Query arguments. Arguments should be in pairs where one is the
        /// name of the parameter and the second is the value. The very last argument can
        /// optionally be a SqlParameter object for specifying a custom argument type</param>
        /// <returns></returns>
        public SqlCommand CreateCommand(string qry, CommandType type, params object[] args)
        {
            SqlCommand cmd = new SqlCommand(qry, _conn);

            // Associate with current transaction, if any
            if (_trans != null)
                cmd.Transaction = _trans;

            // Set command type
            cmd.CommandType = type;

            // Construct SQL parameters
            for (int i = 0; i < args.Length; i++)
            {
                if (args[i] is string && i < (args.Length - 1))
                {
                    SqlParameter parm = new SqlParameter();
                    parm.ParameterName = (string)args[i];
                    parm.Value = args[++i];
                    cmd.Parameters.Add(parm);
                }
                else if (args[i] is SqlParameter)
                {
                    cmd.Parameters.Add((SqlParameter)args[i]);
                }
                else throw new ArgumentException("Invalid number or type of arguments supplied");
            }
            return cmd;
        }
}
}

Answer 1

我认为由于您同时访问（来自15个单独的线程）静态static SqlConnection _conn的{{1}}成员，因此存在问题。我会从DbHelper课程中删除static SqlConnection _conn成员，因为您正在DbHelper进行管理。既然你写的是这个：

Function1

在使用结束时，正在处理SqlConnection con。在另一个线程中，可能会发生Funtion1正在调用 con.Open（）; 从而产生空指针引用。

对象引用未设置为con.Open（）上的对象实例;

1 个答案: