ameblo.over-update.download

• Jun 20, 2014  ASP.NET Forums / Data Access / ADO.NET, Entity Framework, LINQ to SQL, NHibernate / Auto Increment (Identity) does not work in Entity Framework Auto Increment (Identity) does not work in Entity Framework Answered RSS.
• AUTO INCREMENT Field. Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table. Often this is the primary key field that we would like to be created automatically every time a new record is inserted.

• Linq To Sql If Statement

I am designing a table and I have decided to create an auto-generated primary key value as opposed to creating my own scheme or using natural keys. I see that SQL Server offers globally unique identifiers (GUIDs) as well as identities to create these valu. Updating an existing AUTOINCREMENT column value also resets the AUTOINCREMENT sequence. You can retrieve the most recent automatically generated AUTOINCREMENT value with the LASTINSERTID SQL function or the mysqlinsertid C API function. These functions are connection-specific, so their return values are not affected by another.

A primary key in a relational database is a column or combination of columns that always contain unique values. Knowing the primary key value allows you to locate the row that contains it. Relational database engines, such as SQL Server, Oracle, and Microsoft Access/Jet support the creation of automatically incrementing columns that can be designated as primary keys. These values are generated by the server as rows are added to a table. In SQL Server, you set the identity property of a column, in Oracle you create a Sequence, and in Microsoft Access you create an AutoNumber column.

A DataColumn can also be used to generate automatically incrementing values by setting the AutoIncrement property to true. However, you might end up with duplicate values in separate instances of a DataTable, if multiple client applications are independently generating automatically incrementing values. Having the server generate automatically incrementing values eliminates potential conflicts by allowing each user to retrieve the generated value for each inserted row.

During a call to the Update method of a DataAdapter, the database can send data back to your ADO.NET application as output parameters or as the first returned record of the result set of a SELECT statement executed in the same batch as the INSERT statement. ADO.NET can retrieve these values and update the corresponding columns in the DataRow being updated.

Some database engines, such as the Microsoft Access Jet database engine, do not support output parameters and cannot process multiple statements in a single batch. When working with the Jet database engine, you can retrieve the new AutoNumber value generated for an inserted row by executing a separate SELECT command in an event handler for the RowUpdated event of the DataAdapter.

Note

An alternative to using an auto incrementing value is to use the NewGuid method of a Guid object to generate a GUID, or globally unique identifier, on the client computer that can be copied to the server as each new row is inserted. The NewGuid method generates a 16-byte binary value that is created using an algorithm that provides a high probability that no value will be duplicated. In a SQL Server database, a GUID is stored in a uniqueidentifier column which SQL Server can automatically generate using the Transact-SQL NEWID() function. Using a GUID as a primary key can adversely affect performance. SQL Server provides support for the NEWSEQUENTIALID() function, which generates a sequential GUID that is not guaranteed to be globally unique but that can be indexed more efficiently.

I am so happy about this because i got mine last week and I have used it to get $100,000. Zoosk coin generator activation key free.

Retrieving SQL Server Identity Column Values

When working with Microsoft SQL Server, you can create a stored procedure with an output parameter to return the identity value for an inserted row. The following table describes the three Transact-SQL functions in SQL Server that can be used to retrieve identity column values.

The following stored procedure demonstrates how to insert a row into the Categories table and use an output parameter to return the new identity value generated by the Transact-SQL SCOPE_IDENTITY() function.

The stored procedure can then be specified as the source of the InsertCommand of a SqlDataAdapter object. The CommandType property of the InsertCommand must be set to StoredProcedure. The identity output is retrieved by creating a SqlParameter that has a ParameterDirection of Output. When the InsertCommand is processed, the auto-incremented identity value is returned and placed in the CategoryID column of the current row if you set the UpdatedRowSource property of the insert command to UpdateRowSource.OutputParameters or to UpdateRowSource.Both.

If your insert command executes a batch that includes both an INSERT statement and a SELECT statement that returns the new identity value, then you can retrieve the new value by setting the UpdatedRowSource property of the insert command to UpdateRowSource.FirstReturnedRecord.

Merging New Identity Values

A common scenario is to call the GetChanges method of a DataTable to create a copy that contains only changed rows, and to use the new copy when calling the Update method of a DataAdapter. This is especially useful when you need to marshal the changed rows to a separate component that performs the update. Following the update, the copy can contain new identity values that must then be merged back into the original DataTable. The new identity values are likely to be different from the original values in the DataTable. To accomplish the merge, the original values of the AutoIncrement columns in the copy must be preserved, in order to be able to locate and update existing rows in the original DataTable, rather than appending new rows containing the new identity values. However, by default those original values are lost after a call to the Update method of a DataAdapter, because AcceptChanges is implicitly called for each updated DataRow.

There are two ways to preserve the original values of a DataColumn in a DataRow during a DataAdapter update:

• The first method of preserving the original values is to set the AcceptChangesDuringUpdate property of the DataAdapter to false. This affects every DataRow in the DataTable being updated. For more information and a code example, see AcceptChangesDuringUpdate.

• The second method is to write code in the RowUpdated event handler of the DataAdapter to set the Status to SkipCurrentRow. The DataRow is updated but the original value of each DataColumn is preserved. This method enables you to preserve the original values for some rows and not for others. For example, your code can preserve the original values for added rows and not for edited or deleted rows by first checking the StatementType and then setting Status to SkipCurrentRow only for rows with a StatementType of Insert.

When either of these methods is used to preserve original values in a DataRow during a DataAdapter update, ADO.NET performs a series of actions to set the current values of the DataRow to new values returned by output parameters or by the first returned row of a result set, while still preserving the original value in each DataColumn. First, the AcceptChanges method of the DataRow is called to preserve the current values as original values, and then the new values are assigned. Following these actions, DataRows that had their RowState property set to Added will have their RowState property set to Modified, which may be unexpected.

Linq To Sql If Statement

How the command results are applied to each DataRow being updated is determined by the UpdatedRowSource property of each DbCommand. This property is set to a value from the UpdateRowSource enumeration.

The following table describes how the UpdateRowSource enumeration values affect the RowState property of updated rows.

Example

This example demonstrates extracting changed rows from a DataTable and using a SqlDataAdapter to update the data source and retrieve a new identity column value. The InsertCommand executes two Transact-SQL statements; the first one is the INSERT statement, and the second one is a SELECT statement that uses the SCOPE_IDENTITY function to retrieve the identity value.

The UpdatedRowSource property of the insert command is set to UpdateRowSource.FirstReturnedRow and the MissingSchemaAction property of the DataAdapter is set to MissingSchemaAction.AddWithKey. The DataTable is filled and the code adds a new row to the DataTable. The changed rows are then extracted into a new DataTable, which is passed to the DataAdapter, which then updates the server.

The OnRowUpdated event handler checks the StatementType of the SqlRowUpdatedEventArgs to determine if the row is an insert. If it is, then the Status property is set to SkipCurrentRow. The row is updated, but the original values in the row are preserved. In the main body of the procedure, the Merge method is called to merge the new identity value into the original DataTable, and finally AcceptChanges is called.

Dec 19, 2019  MikroTik RouterOS License 2020 Download the Completes Installation. If you want to take advantage of the excellent features of the operating system of the MikroTik license key crack, it is also good to have a premium version. Indeed, the free version does not offer all the functions. May 29, 2018  MikroTik Crack is the latest Latvian computer manufacturing equipment which is used for sells wireless products and routers founded in 1996. MikroTik License key is the latest and amazing Latvian computer manufacturing networking equipment founded in 1996 for advanced routers and ISP wireless products. Apr 17, 2018  MikroTik RouterOS License Key Generator Free Download. MikroTik RouterOS 6.42 Crack for mac and windows represents the working system of the MikroTik RouterBoard units and it’ll permit customers to additionally set up it individually on their techniques and switch them into totally useful routers.Folks will then be capable to entry a number of options that may allow them router. Mikrotik 5 license key generator online. Apr 08, 2018  Mikrotik 6.33 Crack + License Key Generator. Mikrotik Crack is advance technology routers system which is developed with specula structures and tools to work with special perspective of Intel and Core pcs.This is a RouterOS system which is broadly used in the world.It automatically starts work and then converts your simple computer into an electronic router which performs the same functions of. Mar 24, 2020  MikroTik RouterOS v6 Serial key is best for the clients who constantly drew in with web utilization. It’s well-disposed UI and use is amazing than other switch working framework. Experts and switch administrators loved MikroTik RouterOS 6 Keygen’s execution and effectiveness. MikroTik RouterOS 7.1 beta 5 Crack Features.

Retrieving Microsoft Access Autonumber Values

This section includes a sample that shows how to retrieve Autonumber values from a Jet 4.0 database. The Jet database engine does not support the execution of multiple statements in a batch or the use of output parameters, so it is not possible to use either of these techniques to return the new Autonumber value assigned to an inserted row. However, you can add code to the RowUpdated event handler that executes a separate SELECT @@IDENTITY statement to retrieve the new Autonumber value.

Example

Instead of adding schema information using MissingSchemaAction.AddWithKey, this example configures a DataTable with the correct schema prior to calling the OleDbDataAdapter to fill the DataTable. In this case, the CategoryID column is configured to decrement the value assigned each inserted row starting from zero, by setting AutoIncrement to true, AutoIncrementSeed to 0, and AutoIncrementStep to -1. The code then adds two new rows and uses GetChanges to add the changed rows to a new DataTable that is passed to the Update method.

The RowUpdated event handler uses the same open OleDbConnection as the Update statement of the OleDbDataAdapter. It checks the StatementType of the OleDbRowUpdatedEventArgs for inserted rows. For each inserted row a new OleDbCommand is created to execute the SELECT @@IDENTITY statement on the connection, returning the new Autonumber value, which is placed in the CategoryID column of the DataRow. The Status property is then set to UpdateStatus.SkipCurrentRow to suppress the hidden call to AcceptChanges. In the main body of the procedure, the Merge method is called to merge the two DataTable objects, and finally AcceptChanges is called.

Retrieving Identity Values

We often set the column as identity when the values in the column must be unique. And sometimes we need the identity value of new data. This sample demonstrates how to retrieve identity values:

• Creates a stored procedure to insert data and return an identity value.

• Executes a command to insert the new data and display the result.

• Uses SqlDataAdapter to insert new data and display the result.

Before you compile and run the sample, you must create the sample database, using the following script:

The code listing follows:

Tip

The code listing refers to an Access database file called MySchool.mdb. You can download MySchool.mdb (as part of the full C# or Visual Basic sample project) from code.msdn.microsoft.com.

See also

Re: ASP.NET Dynamic Data + guid

Mar 24, 2010 05:32 PMjcilibertiLINK

First of all, All this should work out-of-box. At this point I would not recommend building a production system on this stuff until they get it to a point where things work as one would expect. What we are trying to do here is some real basic stuff. I never heard of anyone having these kinds of issues with Powerbuilder

Anyway,

Here is the work around I came up with for Entity Framework:

First I define the following interface:

interface IAutoGeneratePrimaryKey
{
void GenerateKey();
}

Note: It is not DBAutoGenerate. We can't do this because when we set things as PrimaryKey entity framework will make the field non-nullible. So in other words, you cannot set the value to null and have the DB create the value.

Next I create a partial class for my entities and create an event handler for SavingChanges. In the event handler I check for objects that have been added and if they implement the IAutoGeneratePrimaryKey interface I call the GenerateKey() method.

public partial class Entities1
{
partial void OnContextCreated()
{
SavingChanges += new EventHandler(Entities1_SavingChanges);
}
void Entities1_SavingChanges(object sender, EventArgs e)
{
ObjectContext objectContext = (ObjectContext)sender;
var objectStateManager = objectContext.ObjectStateManager;
IEnumerable<ObjectStateEntry> objectStates = objectStateManager.GetObjectStateEntries(EntityState.Added);
foreach (var objectState in objectStates)
{
object entity = objectState.Entity;
IAutoGeneratePrimaryKey autoObj = entity as IAutoGeneratePrimaryKey;
if (autoObj != null)
{
autoObj.GenerateKey();
}
}
}
}

The last step is to have each of your entities that need to generate a primary key implement the interface.

[MetadataType(typeof(Project_Metadata))]
[ScaffoldTable(true)]
public partial class Project : IAutoGeneratePrimaryKey
{
public void GenerateKey()
{
ProjectId = Guid.NewGuid();
}
}
public class Project_Metadata
{
[ScaffoldColumn(false)]
public object ProjectId;
}