Tài liệu Connecting to a Microsoft Excel Workbook ppt

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Recipe 1.2 Connecting to a Microsoft Excel Workbook
Problem
You want to access data stored in a Microsoft Excel workbook.
Solution
Use the OLE DB Jet provider to create, access, and modify data stored in an Excel
workbook.
The sample code contains two event handlers:
Form.Load
Creates an OleDbDataAdapter that uses the Jet OLE DB provider to access an
Excel workbook. Custom insert and update logic is created for the DataAdapter. A
DataTable is filled from the first worksheet, Sheet1, in the Excel workbook and
the default view of the table is bound to a data grid on the form.
Update Button.Click
Uses the DataAdapter created in the Form.Load event handler to update the Excel
workbook with the programmatic changes.
The C# code is shown in Example 1-2
.
Example 1-2. File: ExcelForm.cs
// Namespaces, Variables, and Constants
using System;
using System.Configuration;
using System.Data;

private OleDbDataAdapter da;
private DataTable dt;

// . . .

private void ExcelForm_Load(object sender, System.EventArgs e)
{
// Create the DataAdapter.
da = new OleDbDataAdapter("SELECT * FROM [Sheet1$]",
ConfigurationSettings.AppSettings["Excel_0115_ConnectString"]);

// Create the insert command.
String insertSql = "INSERT INTO [Sheet1$] " +
"(CategoryID, CategoryName, Description) " +
"VALUES (?, ?, ?)";
da.InsertCommand =
new OleDbCommand(insertSql, da.SelectCommand.Connection);
da.InsertCommand.Parameters.Add("@CategoryID", OleDbType.Integer, 0,
"CategoryID");
da.InsertCommand.Parameters.Add("@CategoryName", OleDbType.Char, 15,
"CategoryName");
da.InsertCommand.Parameters.Add("@Description", OleDbType.VarChar, 100,
"Description");

// Create the update command.
String updateSql = "UPDATE [Sheet1$] " +
"SET CategoryName=?, Description=? " +
"WHERE CategoryID=?";
da.UpdateCommand =
new OleDbCommand(updateSql, da.SelectCommand.Connection);
da.UpdateCommand.Parameters.Add("@CategoryName", OleDbType.Char, 15,
"CategoryName");
da.UpdateCommand.Parameters.Add("@Description", OleDbType.VarChar, 100,
"Description");
da.UpdateCommand.Parameters.Add("@CategoryID", OleDbType.Integer, 0,

"CategoryID");

// Fill the table from the Excel spreadsheet.
dt = new DataTable( );
da.Fill(dt);
// Define the primary key.
dt.PrimaryKey = new DataColumn[] {dt.Columns[0]};

// Records can only be inserted using this technique.
dt.DefaultView.AllowDelete = false;
dt.DefaultView.AllowEdit = true;
dt.DefaultView.AllowNew = true;
// Bind the default view of the table to the grid.
dataGrid.DataSource = dt.DefaultView;
}
private void updateButton_Click(object sender, System.EventArgs e)
{
da.Update(dt);
}
Discussion
You can use the Jet OLE DB provider to access Microsoft Excel as a data source. The Jet
database engine can access other database file formats through Indexed Sequential
Access Method (ISAM) drivers specified in the Extended Properties attribute of the
connection. Excel 2000 and 2002 are supported with the Excel 8.0 source database type
as shown in the following example:
Provider=Microsoft.Jet.OLEDB.4.0;Data Source=myBook.xls;
Extended Properties="Excel 8.0;HDR=YES";
The Extended Properties attribute can, in addition to the ISAM version property, specify
whether or not tables include headers as field names in the first row of a range using an
HDR attribute.

There are three ways in which you can reference Excel workbook data within a SQL
statement:
•
Specify the worksheet name followed by a dollar sign to access the entire range
used in the worksheet:
SELECT * FROM [MySheet$]
•
Specify a range explicitly using cells:
SELECT * FROM [MySheet$A1:E5]
•
Specify a range with a defined name, as shown in the solution:
SELECT * FROM MyRange
The following subsections discuss how to use Excel as an ADO.NET data source.
Create table
The CREATE TABLE command will create a table in an Excel workbook. The
workbook for the connection will be created if it does not exist. For example:
CREATE TABLE MySheet (Field1 char(10), Field2 float, Field3 date)
Create data
You can use the INSERT command, either static or parameterized, to insert data into a
worksheet or range:
INSERT INTO [MySheet$] (Field1, Field2, Field3)
VALUES ('testdata', 1.234, '09/28/1979');
Retrieve data
Use either a DataAdapter or a DataReader to retrieve data from an Excel workbook.
Create a SQL SELECT statement referencing a worksheet or a range in an Excel
workbook and execute the statement to fill a DataSet using a DataAdapter or to create a
DataReader. For example:
SELECT * FROM [MySheet$]
Update data
The UPDATE command, either static or parameterized, can update data in a worksheet or

range. For example:
UPDATE [MySheet$]
SET Field2 = '2.345',
Field3 = '10/18/1964'
WHERE
Field1 = 'testdata'
Delete data
The Jet OLE DB provider does not allow DELETE operations. An error will be raised if
an attempt is made to execute a DELETE statement affecting one or more records.
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