SQL records

9 min

📘 Note With this method, you are working with the lowest set of the Business Foundation APIs. There is no business logic other than SQL data constraints checks. Therefore, do not use this method. See Entity ObjectsEntity Objects for other options for working with data.

Classes in this topic are available in the following namespaces:

Mediachase.BusinessFoundation.Data.Sql

Mediachase.BusinessFoundation.Data.Sql.Management

CustomTableRow class

A CustomTableRow object represents an SQL user row. Use the CustomTableRow object and its properties and methods to retrieve, evaluate, insert, delete, and update the values in the table.

Create a CustomTableRow object, passing the Table object to create a new record. After creating a new CustomTableRow, use the index property to set the column values. Finally, call the Update method of the CustomTableRow object to confirm the addition.

You can delete a row from the table by calling the Delete method of the CustomTableRow object. The removal occurs when you call the Delete method.

Create a record

📘 Note BF supports Integer and Guid as primary keys.

// Create a new book
CustomTableRow newBook = CustomTableRow(bookTable);
newBook["Title"] = "Programming Windows Phone 7";
newBook.Update();
PrimaryKeyId newBookPk = newBook.PrimaryKeyId.Value;

Load a record from a table

You can load a record from a table by creating a CustomTableRow object with primary key id. If the record is not found, an ObjectNotFoundException exception is thrown.

// Load book
PrimaryKeyId bookPk = 1;
CustomTableRow book = new CustomTableRow(bookTable, bookPk);
String title = (String)book["Title"];

Select records from a table

Call the CustomTableRow.List statement to return an array of CustomTableRow objects from the table. The CustomTableRow class has several List methods.

List(Table table) – Returns records from table.

List(Table table, params SortingElement[] sorting) – Returns records from table sorted by specified sorting elements.

List(Table table, params FilterElement[] filters) – Returns filtered records by specified filters.

List(Table table, FilterElementCollection filters, SortingElementCollection sorting) – Returns filtered records by specified filters and sorted by specified sorting elements.

List(Table table, FilterElementCollection filters, SortingElementCollection sorting, int start, int count) – Returns records at a specified position and a specified count only.

See Filter and sortFilter and sort.

Get the total records count

Call the CustomTableRow.GetTotalCount statement to return the total record count.

Extended methods

You can use the extended CustomTableRow.GetReader and CustomTableRow.GetTable methods to get records in the inner .NET formats.

Delete a row

To delete a row from a table, call the Delete method of the CustomTableRow object. The removal occurs when you call the Delete method.

// Step 1. Load book
PrimaryKeyId bookPk = 1;
CustomTableRow book = new CustomTableRow(bookTable, bookPk);

// Step 2. Delete book
book.Delete();

Use the CustomTableRow.Delete static method to delete rows without row loading.

Example: Deleting rows without reloading:

CustomTableRow.Delete(new TableConfig(bookTable), bookPk);

Transaction

Upon instantiating a SqlTransactionScope by calling SqlContext.BeginTransaction statement, the transaction manager determines which transaction to participate in. When determined, the scope always participates in that transaction. You can obtain a reference to the ambient transaction by calling the TransactionScope property of the SqlContext class.

If no exception occurs within the transaction scope (that is, between the initialization of the SqlTransactionScope object and the calling of its Dispose method), the transaction in which the scope participates is allowed to proceed. If an exception occurs within the transaction scope, the transaction in which it participates is rolled back.

When your application completes work it wants to perform in a transaction, you should call the Commit method once to inform the transaction manager that it can commit the transaction. Failing to call this method aborts the transaction.

A call to the Dispose method marks the end of the transaction scope. Exceptions that occur after calling this method may not affect the transaction.

A call to the AddCallback method registers a custom callback. You can use a transaction callback to handle final transaction commit or rollback.

Example: Initialize the SQL Metamodel:

using (SqlContext.Current = new SqlContext(connectionString))
{
  using (SqlTransactionScope tran = SqlContext.Current.BeginTransaction())
  {
    // Step 1. Get Book table
    Table bookTable = SqlContext.Current.Database.Tables["Book"];

    // Step 2. Create a new book
    CustomTableRow newBook = new CustomTableRow(bookTable);
    newBook["Title"] = "Programming Windows Phone 7";
    newBook.Update();

    PrimaryKeyId newBookPk = newBook.PrimaryKeyId.Value;

    // Step N. Call Commit to commit transaction
    tran.Commit();
  }
}

SqlBlobStream class

A SqlBlobStream object exposes a Stream around a text, ntext, or image column, supporting both synchronous and asynchronous read and write operations.

To reduce the amount of memory used when writing a BLOB value, a common practice is to write the BLOB to the database in chunks. The process of writing a BLOB to a database in this way depends on the capabilities of your database.

Use the SqlBlobStream class to read, write, create or close text, ntext, or image values from a text, ntext, or image column, and to manipulate other file-related operating system handles, such as file.

SqlBlobStream objects support random access to files using the Seek method. Seek allows the read/write position to be moved to any position within the file. This is done with byte offset reference point parameters. The byte offset is relative to the seek reference point, which can be the beginning, the current position, or the end of the underlying file, as represented by the three properties of the SeekOrigin class.

Example: Using the SqlBlobStream class:

strConnectionString = "Data source=(local);Initial catalog=TestDB;User Id=sa;Password=";
string strSqlTable = "Files";
string strBLOBColumn = "Data";

try
{
  using(SqlBlobStream stream = new SqlBlobStream(strConnectionString,
  strSqlTable,
  strBLOBColumn,
  SqlBlobAccess.Read, new SqlParameter("@FileId", 12345)))
  {
    byte[] tmpBuffer = new byte[1024];
    int Length = 0;
    while ((Length = stream.Read(tmpBuffer, 0, 1024)) == 1024)
    {
      //Save tmpBuffer
    }
  }
}
catch (Exception ex)
{
  System.Diagnostics.Trace.WriteLine(ex);
  throw;
}