C#SQL连接类连接问题中的字符串

所以我注意到在我的代码中我有很多重复的连接字符串,并决定将其清理一下.

我的问题是,现在我已将连接字符串放入单独的类中,我在使用时无法再打开连接 using (InfoTableConnection = new SqlConnection(infoTableConnString))

但是,如果我不使用using它工作正常.

我猜,我不太了解它是如何工作的.这是我的代码,如果有人可以解释一旦它被引入一个类和/或如何修复它究竟发生了什么.

连接类:Connection.cs

class Connection
    {
        public static SqlConnection InfoTableConnection = null;
        public void InfoConnection()
        {
            string infoTableConnString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MTRInfoTables;Integrated Security=True";

            using (InfoTableConnection = new SqlConnection(infoTableConnString))

            InfoTableConnection.Open();

        }
    }

示例代码来自: MainForm.cs

private void zGradeCombo()
        {
            try
            {

                //Connection string from class.
                Connection connInfoTable = new Connection();
                connInfoTable.InfoConnection();

                SqlCommand cmd = new SqlCommand();
                cmd.Connection = Connection.InfoTableConnection;
                cmd.CommandText = "SELECT * FROM [dbo].[Item] ORDER by [Type] ASC";

                SqlDataReader reader = cmd.ExecuteReader();

                while (reader.Read())
                {
                    cmbType.Items.Add(reader["Type"].ToString());
                }

                //Close connection from "Connection" class
                Connection.InfoTableConnection.Close();
            }

            //Catch Exception
            catch (Exception ex)
            {
                MessageBox.Show(this, ex.Message, "SQL ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

SirBirne.. 5

using关键字确保在到达范围末尾时处理对象,以便之后清理所有资源

using (InfoTableConnection = new SqlConnection(infoTableConnString))
{
        InfoTableConnection.Open();
} // <- At this point InfoTableConnection will be disposed (and closed) 

因为你关心在你周围的代码中处理你不需要在类的构造函数中使用using块.但是在Connection类上实现IDisposable并使用它是一个好主意:

using(var con = new Connection())
{
    SqlCommand cmd = new SqlCommand();
    cmd.Connection = con.InfoTableConnection;
    cmd.CommandText = "SELECT * FROM [dbo].[Item] ORDER by [Type] ASC";

    SqlDataReader reader = cmd.ExecuteReader();

    while (reader.Read())
    {
        cmbType.Items.Add(reader["Type"].ToString());
    }
}

在Dispose()连接方法中,您应该处置SQL连接.

using关键字确保在到达范围末尾时处理对象,以便之后清理所有资源

using (InfoTableConnection = new SqlConnection(infoTableConnString))
{
        InfoTableConnection.Open();
} // <- At this point InfoTableConnection will be disposed (and closed) 

因为你关心在你周围的代码中处理你不需要在类的构造函数中使用using块.但是在Connection类上实现IDisposable并使用它是一个好主意:

using(var con = new Connection())
{
    SqlCommand cmd = new SqlCommand();
    cmd.Connection = con.InfoTableConnection;
    cmd.CommandText = "SELECT * FROM [dbo].[Item] ORDER by [Type] ASC";

    SqlDataReader reader = cmd.ExecuteReader();

    while (reader.Read())
    {
        cmbType.Items.Add(reader["Type"].ToString());
    }
}

在Dispose()连接方法中,您应该处置SQL连接.