title: SQL Server connect error: Instance failure
body: <p>I'm trying to insert data from excel file into a column of sql database.</p>
  
  <pre><code>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!");
      }
  </code></pre>
  
  <p>web config :</p>
  
  <pre><code>   &lt;connectionStrings&gt;
    &lt;add name="ExcelCon" connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\John\\Desktop\\ExcelFile.xlsx;Extended Properties=Excel 12.0"/&gt;
    &lt;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;"/&gt;
    &lt;add name="ConnectionString" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True"
          providerName="System.Data.SqlClient" /&gt;
  &lt;/connectionStrings&gt;
  </code></pre>
  
  <p>The problem is I'm getting this error and I don't know why:</p>
  
  <pre><code>Exception Details: System.InvalidOperationException: Instance failure.
  here:sqlcon.Open();
  </code></pre>