Entity Framework elementary Article 7-basic operations: add, update, delete, and transaction

In this sectionCodeTo learn. These basic operations are relatively simple. The content related to these basic operations is described in sections 1 to 6.

LAdded:

Method 1: UseAddtoxxx (XXX)Method: The instance code is as follows:

Using(VaREDM =New Northwindentities())

{

MERsC =New MERs{Customerid ="C #", City =" Chengdu" , Address =" Sichuan, China" , CompanyName ="Cnblogs", Country =" China" , Fax ="10086", Phone ="1008611", Postalcode ="610000", Region =" Tianfu Square" , Contactname =" Windmill. Net" };

EDM. addtocustomers (C );

IntResult = EDM. savechanges ();

Assert. Areequal (result, 1 );

MERsADDC = EDM. Customers. firstordefault (Cc => cc. customerid ="C #");

Console. Writeline ("Customerid = {0}, city = {1 }", ADDC. customerid, ADDC. City );

}

Method 2: UseObjectcontextOfAddobject (String entitysetname,ObjectEntity)Method. The instance code is as follows:

Using(VaREDM =New Northwindentities())

{

MERsC =New MERs{Customerid ="C2", City =" Chengdu 2" , Address =" Sichuan, China 2" , CompanyName ="Cnblogs", Country =" China" , Fax ="10086", Phone ="1008611", Postalcode ="610000", Region =" Tianfu Square" , Contactname =" Windmill. Net" };

EDM. addobject ("MERs", C );

IntResult = EDM. savechanges ();

Assert. Areequal (result, 1 );

MERsADDC = EDM. Customers. firstordefault (Cc => cc. customerid ="C2");

Console. Writeline ("Customerid = {0}, city = {1 }", ADDC. customerid, ADDC. City );

}

In the code, note that the parameter "entitysetname" in the addobject method refers to the corresponding object name, which should be:"MERs", Not"Northwindentities. MERs";

LUpdate:

Using(VaREDM =New Northwindentities())

{

MERsADDC = EDM. Customers. firstordefault (Cc => cc. customerid ="C2");

ADDC. City ="Cd";

ADDC. contactname ="Cnblogs";

ADDC. Country ="Cn";

IntResult = EDM. savechanges ();

Assert. Areequal (result, 1 );

MERsUpdatec = EDM. Customers. firstordefault (Cc => cc. customerid ="C2");

Console. Writeline ("Customerid = {0}, city = {1 }", Updatec. customerid, updatec. City );

}

Note that the primary key cannot be updated; otherwise,"System. invalidoperationexception:The property "XXX" is part of the key information of the object and cannot be modified."

LDelete:

The instance code is as follows:

Using(VaREDM =New Northwindentities())

{

MERsDeletec = EDM. Customers. firstordefault (Cc => cc. customerid ="C2");

EDM. deleteobject (deletec );

IntResult = EDM. savechanges ();

Assert. Areequal (result, 1 );

MERsC = EDM. Customers. firstordefault (Cc => cc. customerid ="C2");

Assert. Areequal (C,Null);

}

LTransaction:

The instance code is as follows:

NorthwindentitiesEDM =Null;

System. Data. Common.DbtransactionTRAN =Null;

Try

{

EDM =New Northwindentities();

EDM. Connection. open ();

TRAN = EDM. Connection. begintransaction ();

MERsCST = EDM. Customers. firstordefault (Cc => cc. customerid ="C #");

CST. Country ="Cn";

CST. City ="Cd";

EDM. savechanges ();

Tran. Commit ();

}

Catch(ExceptionEx)

{

If(Tran! =Null)

Tran. rollback ();

ThrowEx;

}

Finally

{

If(EDM! =Null& EDM. Connection. State! = System. Data.Connectionstate. Closed)

EDM. Connection. Close ();

}

now, the basic introduction is complete. Later, I plan to write some intermediate articles.