在Visual Studio 2015中连接到数据库

Question

This is going to be simple/stupid question.

I have installed Visual studio 2015 Enterprise and created a class Library project with Framework 4.6. But I am not able to find [System.Data].

I want to connect to SQL server using SqlConnection and SqlCommand like object. IntelliSense is not working. I am not able to find example on Google. Every example I have found is related to framework 4.0., but I am used to working with Visual Studio 2010.

Update: ooops
Friends, I found that it was it was using project web-->Class library when I tried Windows-->Class Library project, it was all there. But still I want to know the difference.... Now another problem is that I am not able to add reference this project in web project. It is giving some Dependency NewBLL>=1.0.0-* could not be resolved.

Answer 1

The project template for a class library adds a reference to System.Data automatically.

Try adding the following statement to the top of the class file:

using System.Data.SqlClient;

Answer 2

Answering this seems foolish as there are a plethora of examples from just a simple Google search... maybe I can help you along your way. Please note this question will most likely be down-voted for duplication.

For this particular scenario you are wanting to utilize SqlClient which as previously mentioned lives under System.Data which fully qualifies to System.Data.SqlClient .

using System.Data.SqlClient;

Once you have imported the namespace (not required, just prevents you from having to fully qualify everything) you may start working with the classes contained within. The two we need to focus on are SqlConnection and SqlCommand .

SqlConnection is the class actually used to connect to a particular database. It has several different constructors, but you may instantiate a new instance like this utilizing the default constructor:

SqlConnection connection = new SqlConnection();

It is more common to provide the connection string within the constructor, but you may do so afterwards through the ConnectionString property. Now digressing just slightly we should wrap the object in a using statement to prevent unmanaged resources from hanging around in memory:

using(SqlConnection connection = new SqlConnection()) 
{

} //<--object is disposed of at the end of the code block.

Read about the using statement https://msdn.microsoft.com/en-us/library/yh598w02.aspx and you may also look at IDisposable https://msdn.microsoft.com/en-us/library/system.idisposable(v=vs.110).aspx if necessary.

Once you have a connection you may now instantiate a SqlCommand object using the same... well using statement:

using(SqlConnection connection = new SqlConnection())
{
    using(SqlCommand command = new SqlCommand())
    {

    }
}

Usually with SqlCommand you would supply the connection to it as well as command text to query against the SQL Server database. Finally you execute the command with:

command.ExecuteNonQuery();

Please understand that I have purposely left out some of the details to allow you to research each individual class and obtain a more thorough understanding of what needs to be done.

SqlConnection Class https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection(v=vs.110).aspx

SqlCommand Class https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand(v=vs.110).aspx

ConnectionString Property https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring(v=vs.110).aspx

Answer 3

Make sure you add normal class Library not class Library (package)