SQL Server连接错误：实例失败

Question

我想从excel文件插入数据到一列sql数据库。

protected void Button1_Click(object sender, EventArgs e) 
    { 
     using (OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["ExcelCon"].ConnectionString)) 
     { 
      con.Open(); 
      OleDbCommand com = new OleDbCommand("Select * from [Sheet1$]", con); 
      OleDbDataReader dr = com.ExecuteReader(); 
      using (SqlConnection sqlcon = new SqlConnection(ConfigurationManager.ConnectionStrings["Sql"].ConnectionString)) 
      { 
       sqlcon.Open(); 
       using (SqlBulkCopy bulkCopy = new SqlBulkCopy(sqlcon)) 
       { 
        bulkCopy.ColumnMappings.Add("ExcelColumnHeaderName", "SqlColumnName"); 
        bulkCopy.DestinationTableName = "tableName"; 
        bulkCopy.WriteToServer(dr); 
       } 
      } 
      dr.Close(); 
      dr.Dispose(); 
     } 
     Response.Write("Upload Successfull!"); 
    } 

web配置：

<connectionStrings> 
    <add name="ExcelCon" connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\John\\Desktop\\ExcelFile.xlsx;Extended Properties=Excel 12.0"/> 
    <add name="Sql" connectionString="Data Source=.\\SQLEXPRESS;AttachDbFilename='c:\\users\\John\\documents\\visual studio 2010\\Projects\\WebApplication3\\WebApplication3\\App_Data\\Database1.mdf';Integrated Security=True;User Instance=True;"/> 
    <add name="ConnectionString" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True" 
     providerName="System.Data.SqlClient" /> 
</connectionStrings> 

问题是，我得到这个错误，我不知道为什么：

Exception Details: System.InvalidOperationException: Instance failure. 
here:sqlcon.Open(); 

Answer 1

从连接字符串中删除双斜线。