Overcoming Keyword Conflicts When Using CommandBuilders

Solution Use the QuotePrefix and QuoteSuffix properties of the CommandBuilder object to delimit database server object names containing spaces or other illegal characters.. The sample c

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Recipe 4.14 Overcoming Keyword Conflicts When Using CommandBuilders

Problem

Your data includes table and column names that conflict with SQL keywords You can overcome this with brackets or quotes in SELECT statements that you write, but the CommandBuilder creates illegal update statements You need to know how to use the CommandBuilder with your data

Solution

Use the QuotePrefix and QuoteSuffix properties of the CommandBuilder object to

delimit database server object names containing spaces or other illegal characters

The sample code contains two event handlers:

Preview Button.Click

Displays the delete, insert, and update commands using the delimiters specified by the user for the QuotePrefix and QuoteSuffix properties, and either the OLE DB or SQL Server data provider as specified by the user

Retrieve OLE DB Button.Click

Uses the GetOleDbSchemaTable( ) method of the OleDbConnection object to retrieve the default prefix and suffix delimiters for the data source

The C# code is shown in Example 4-33

Example 4-33 File: CommandBuilderKeywordConflictForm.cs

// Namespaces, variables, and constants

using System;

using System.Configuration;

using System.Data;

using System.Data.SqlClient;

using System.Data.OleDb;

//

private void previewButton_Click(object sender, System.EventArgs e)

{

String sqlText = "SELECT OrderID, ProductID, Quantity, " +

"UnitPrice, Discount FROM [Order Details]";

if (oleDbRadioButton.Checked)

{

// Build the DataAdapter and the CommandBuilder

OleDbDataAdapter da = new OleDbDataAdapter(sqlText,

ConfigurationSettings.AppSettings["OleDb_ConnectString"]);

OleDbCommandBuilder cb = new OleDbCommandBuilder(da);

// Set the prefix and suffix

cb.QuotePrefix = quotePrefixTextBox.Text;

cb.QuoteSuffix = quoteSuffixTextBox.Text;

// Display CommandBuilder commands with the prefix and suffix

resultTextBox.Text =

"DeleteCommand: " + cb.GetDeleteCommand( ).CommandText + Environment.NewLine + Environment.NewLine +

"InsertCommand: " + cb.GetInsertCommand( ).CommandText +

Environment.NewLine + Environment.NewLine +

"UpdateCommand: " + cb.GetUpdateCommand( ).CommandText; }

else

{

// Build the DataAdapter and the CommandBuilder

SqlDataAdapter da = new SqlDataAdapter(sqlText,

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

SqlCommandBuilder cb = new SqlCommandBuilder(da);

// Set the prefix and suffix

cb.QuotePrefix = quotePrefixTextBox.Text;

cb.QuoteSuffix = quoteSuffixTextBox.Text;

// Display CommandBuilder commands with the prefix and suffix

resultTextBox.Text =

"DeleteCommand: " + cb.GetDeleteCommand( ).CommandText + Environment.NewLine + Environment.NewLine +

"InsertCommand: " + cb.GetInsertCommand( ).CommandText +

Environment.NewLine + Environment.NewLine +

"UpdateCommand: " + cb.GetUpdateCommand( ).CommandText; }

}

private void retrieveOleDbButton_Click(object sender, System.EventArgs e)

{

// Retrieve the quote prefix and suffix for the server

OleDbConnection conn = new OleDbConnection(

ConfigurationSettings.AppSettings["OleDb_ConnectString"]);

conn.Open( );

DataTable tableSchema =

conn.GetOleDbSchemaTable(OleDbSchemaGuid.DbInfoLiterals,

new object[] {});

conn.Close( );

// Set the primary key to enable find on LiteralName column

tableSchema.PrimaryKey =

new DataColumn[] {tableSchema.Columns["LiteralName"]};

// Get the prefix and suffix from the OleDbLiteral enumeration

DataRow row;

row = tableSchema.Rows.Find("Quote_Prefix");

quotePrefixTextBox.Text =

((row == null) ? "" : row["LiteralValue"].ToString( ));

row = tableSchema.Rows.Find("Quote_Suffix");

quoteSuffixTextBox.Text =

((row == null) ? "" : row["LiteralValue"].ToString( ));

}

Discussion

The QuotePrefix and QuoteSuffix properties of the CommandBuilder object specify the beginning and ending characters used to delimit database server object names, such as tables and columns in the updating commands generated by the CommandBuilder This is necessary when the object names contain special characters or reserved tokens;

otherwise, the commands will fail when executed

For example, in SQL Server 2000 and later, database object names can contain any valid Microsoft Windows NT/2000/XP character including spaces and punctuation marks T-SQL is more restrictive with identifiers that can be used without delimiters You can use QuotePrefix and QuoteSuffix to delimit the SQL Server object names when required by T-SQL

The QuotePrefix and QuoteSuffix values have no effect on the CommandText of

SelectCommand These delimiters must be specified as part of the SelectCommand that the CommandBuilder is based on

The default values for QuotePrefix and QuoteSuffix are empty strings

The example demonstrates using QuotePrefix and QuoteSuffix with both the OLE DB and SQL Server CommandBuilder objects As you can see, they function nearly

identically

The CommandBuilder makes it easy to update the data source with changes made to the DataSet Update logic is created automatically

so no understanding is required of how to code the actual delete, insert, and update SQL statements The CommandBuilder drawbacks include slower performance because of the time that it takes to

request metadata and construct the updating logic, updates that are limited to simple single-table scenarios, and a lack of support for stored procedures Because of these drawbacks, the CommandBuilder

is seldom used in enterprise application development

The example also demonstrates retrieving the default quote prefix and suffix from the database server The GetOleDbSchemaTable( ) method of the OleDbConnection object returns schema information from a data source based on a GUID argument indicating one

of the OleDbSchemaGuid values The value DbInfoLiterals returns a list of provider-specific literals used in text commands The literals are returned as a table of rows

Within this table, there is a column named LiteralName The rows containing the default values for the quote prefix and suffix are identified by a LiteralName value of

Quote_Prefix and Quote_Suffix, respectively The actual values are stored in the

LiteralValue column

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