C# – connection leak issue in SQL Server

ado.netcnetsql serversql-server-2008

I am using SQL Server 2008 Enterprise + C# + ADO.Net + .Net 3.5. I am using connection pool at ADO.Net client side (the default behavior of ADO.Net). I am using sp_who2 or sys.dm_exec_connections to find active connections numbers (let me know if my method to find active connection numbers are wrong).

If each time after I create and open a new ADO.Net connection object, I will have a matched close statement to close the ADO.Net connection object instance after using the connection object (to execute store procedure), I am wondering in this scenario, the active connection number should always be 0 after I close all connection from my ADO.Net client application, and if show active connection number > 0, it should be very weird?

thanks in advance,
George

Best Answer

Not so, the ADO.NET connection pool will return your connection to the pool after Close is called. The connection may not really be closed at this point. To force the connection to be closed try clearing the pool before closing. Try this and you should see the connection close from the server.

var conn = new SqlConnection("a server goes here");
        conn.Open();

        SqlConnection.ClearAllPools();
        conn.Close();

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Sql – How to return only the Date from a SQL Server DateTime datatype

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @your_date))

for example

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE()))

gives me

2008-09-22 00:00:00.000

Pros:

No varchar<->datetime conversions required
No need to think about locale

Best Answer

Related Solutions

Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

Example:

Notes:

Sql – How to return only the Date from a SQL Server DateTime datatype

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