无法连接到SQL Server，由于的NullReferenceException [英] Cannot connect to Sql server due to NullReferenceException

问题描述

我有一个与登录表单
登录表单开始Windows窗体应用程序已被罚款，过去几年一天，我正在申请
的休息，我得到现在一个错误，
我有两个数据库中的一个DB.mdf和一个MYD.sdf

I have a windows forms application which begins with the Login form The Login form has been fine for past few day while i was working on rest of the application I get an error now that I have two database one DB.mdf and one MYD.sdf

的NullReferenceException是未处理

NullReferenceException was unhandled

对象引用未设置到对象的实例。

Object reference not set to an instance of an object.

有关代码这个特殊行--->

for this particular lines of code --- >

private void button1_Click(object sender, EventArgs e)
    {
        string path=@"C:\Users\Srinath\Documents\Visual Studio 2010\Projects\TESTFEE\TESTFEE\DB.mdf";
SqlConnection con =new SqlConnection(@"Data Source=.\SQLEXPRESS; AttachDbFilename='"+path+"';User Instance=True");

            string constring=ConfigurationManager.ConnectionStrings["ConnectionStringFMS"].ConnectionString;
         //SqlConnection con=new SqlConnection(constring);

        SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) from LOGIN where USERNAME='" + textUser.Text + "' and PASSWORD='" + textPass.Text + "'", con);
        DataTable dt = new DataTable();

        try
        {
            sda.Fill(dt);
            if (dt.Rows[0][0].ToString() == "1")
            {
                this.Hide();
                e1.Show();

            }
            else
            {

                HoldButton();
                MessageBox.Show("Please Enter Your Right Credentials");
            }

        }
        catch (SqlException ex)
        {

            MessageBox.Show(ex.Message);
        }




        }//![The error i get ][1 -]

我使用的配置文件的连接字符串
试过之前，我直接用SqlConnection的连接
我使用SQL Server 2008 R2在管理工作室
我第一次收到了无法连接到默认的数据库inititally
疑惑 - >
是不是因为使用两种不同类型的分贝在一个应用程序
的问题我试着重新安装的SQL Server 2008，但没有使用
请帮忙

I tried using the Configuration File for connection string before i directly used the SqlConnection for connection I am using Sql server 2008 r2 with the Management studio I first recieved the Failed to connect to the default database inititally Doubts - > is it the Problem because of using two different types of db in one application I tried reinstalling sql server 2008 but no use please help

推荐答案

把你的连接字符串中webconfig，如果你有在*密度纤维板放在App_Data文件夹，使用此格式的作品

Put your connection string in webconfig, If you have the *.mdf placed in App_Data folder, using this format works

<connectionStrings>
  <add name="ConnectionName"
    connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|DatabaseName.mdf;Integrated Security=True;User Instance=True"
    providerName="System.Data.SqlClient" />
</connectionStrings>

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