Name

ConnectionString

Synopsis

string connectionString = Connection.ConnectionString;

Returns or sets a string that opens a database connection. The connection string is formatted as a collection of name/value pairs separated by semicolons. These settings can be provider-specific but typically follow certain conventions; they include basics such as the source database name, the location of the database server, and login information. The connection string is case-insensitive, and all blank characters are ignored.

Examples

The first example creates a SqlConnection that accesses a database on the local computer. Some properties of the connection string are set to connect to the Northwind database using integrated security.

SqlConnection conn = new SqlConnection();

conn.ConnectionString = "Data Source = localhost;" +

  "Integrated security = SSPI;Initial Catalog = Northwind";

The following example creates an OleDbConnection. Some properties of the connection string are set to connect to the Northwind database, using integrated security. Note that the information is identical, except for the addition of a Provider setting that specifies what underlying OLE DB provider should be used.

OleDbConnection conn = new OleDbConnection();

Conn.ConnectionString = "Provider = SQLOLEDB;Data Source = localhost;" +

  "Integrated Security = SSPI;Initial Catalog = northwind";

Notes

The ConnectionString property can be set only when the connection is closed. The Connection class provides many read-only properties that correspond to individual pieces of information from the connection string.

Values in the connection string can optionally be delimited by single or double quotes, e.g., name='value' or name="value"). The most common reason to use this approach is when you need to include blank or semicolon characters in a connection string value.

Any variation in a connection string can thwart connection pooling, so be sure to draw connection strings from a fixed location such as a configuration file to ensure consistency, rather than place them directly in code or construct them manually.

When retrieving the ConnectionString property, you will find that the user authentication information is automatically removed, unless you specifically submit the Persist Security Info setting in the connection string with a value of true.

Tip

For a full list of connection string settings and examples of various provider-specific connection strings, see Chapter 3.