Tài liệu Avoiding Referential Integrity docx

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Recipe 6.6 Avoiding Referential Integrity Problems When Updating the Data
Source
Problem
You sometimes get referential integrity errors when you update a DataSet that contains
related parent, child, and grandchild records back to the underlying data source, but want
to perform the update without errors.
Solution
Use one DataAdapter for each DataTable to update the deleted, updated, and inserted
rows as shown in the following example.
The schema of table TBL0606Parent used in this solution is shown in Table 6-2
.
Table 6-2. TBL0606Parent schema
Column name Data type Length Allow nulls?
ParentId int 4 No
Field1 nvarchar 50 Yes
Field2 nvarchar 50 Yes
The schema of table TBL00606Child used in this solution is shown in Table 6-3.
Table 6-3. TBL0606Child schema
Column name Data type Length Allow nulls?
ChildId int 4 No
ParentId int 4 No
Field3 nvarchar 50 Yes
Field4 nvarchar 50 Yes
The schema of table TBL0606Grandchild used in this solution is shown in Table 6-4.
Table 6-4. TBL0606Grandchild schema
Column name Data type Length Allow nulls?
GrandchildId int 4 No
ChildId int 4 No
Field5 nvarchar 50 Yes

Field6 nvarchar 50 Yes
The sample uses 12 stored procedures:
SP0606_GetParent
Used to retrieve a single record from the Parent table if the optional @ParentId
parameter is specified or all Parent records if it is not
SP0606_DeleteParent
Used to delete the record specified by the @ParentId parameter from the Parent
table
SP0606_InsertParent
Used to insert a record into the Parent table and return the ParentId identity value
for the new record
SP0606_UpdateParent
Used to update all field values for the record in the Parent table specified by the
@ParentId input parameter
SP0606_GetChild
Used to retrieve a single record from the Child table if the optional @ChildId
parameter is specified or all Child records if it is not
SP0606_DeleteChild
Used to delete the record specified by the @ChildId parameter from the Child
table
SP0606_InsertChild
Used to insert a record into the Child table and return the ChildId identity value
for the new record
SP0606_UpdateChild
Used to update all field values for the record in the Child table specified by the
@ChildId input parameter
SP0606_GetGrandchild
Used to retrieve a single record from the Grandchild table if the optional
@GrandchildId parameter is specified or all Grandchild records if it is not
SP0606_DeleteGrandchild

Used to delete the record specified by the @GrandchildId parameter from the
Grandchild table
SP0606_InsertGrandchild
Used to insert a record into the Grandchild table and return the GrandchildId
identity value for the new record
SP0606_UpdateGrandchild
Used to update all field values for the record in the Grandchild table specified by
the @GrandchildId input parameter
The sample code contains four event handlers and two methods:
Form.Load
Sets up the sample by creating a DataSet containing the Parent, Child, and
Grandchild DataTable objects. DataRelation objects are created relating the tables.
DataAdapter objects are created for each DataTable and the select, delete, insert,
and update Command objects are specified for each using the custom logic in the
twelve stored procedures used by this solution. The DataAdapter objects are used
to fill the tables in the DataSet. Finally, the default view of the Parent table is
bound to the data grid on the form.
CreateData( )
This method generates a number of rows in the Parent, Child, and Grandchild
DataTable objects as specified by the input parameters of the method.
UpdateData( )
This method uses the DataAdapter for each of the Parent, Child, and Grandchild
DataTable objects to update offline changes back to the database.
Create Data Button.Click
Calls the CreateData( ) to create four Parent records, four Child records for each
Parent, and four Grandchild records for each Child. Finally, the UpdateData( )
method is called to update the database with the new records.
Modify Data Button.Click
Randomly modifies or deletes records from the Parent, Child, and Grandchild
DataTable objects. The CreateData( ) method is called to create two Parent

records, two Child records for each Parent, and two Grandchild records for each
Child. Finally, the UpdateData( ) method is called to update the database with the
offline changes, deletions, and additions.
Delete Data Button.Click
Deletes all records from the Parent DataTable, which then cascades to delete all
Child and Grandchild records clearing all data from the DataSet. Finally, the
UpdateData( ) method is called to update the database with the offline deletions.
The 12 stored procedures are shown in Example 6-8
through Example 6-19.
Example 6-8. Stored procedure: SP0606_GetParent
CREATE PROCEDURE SP0606_GetParent
@ParentId int=null
AS
SET NOCOUNT ON

if @ParentId is not null
begin
select
ParentId,
Field1,
Field2
from
TBL0606Parent
where
ParentId=@ParentId

return 0
end

select

ParentId,
Field1,
Field2
from
TBL0606Parent

return 0
Example 6-9. Stored procedure: SP0606_DeleteParent
CREATE PROCEDURE SP0606_DeleteParent
@ParentId int
AS
SET NOCOUNT ON

delete
from
TBL0606Parent
where
ParentId=@ParentId

return 0
Example 6-10. Stored procedure: SP0606_InsertParent
CREATE PROCEDURE SP0606_InsertParent
@ParentId int output,
@Field1 nvarchar(50)=null,
@Field2 nvarchar(50)=null
AS
SET NOCOUNT ON

insert TBL0606Parent(
Field1,

Field2)
values (
@Field1,
@Field2)

if @@rowcount=0
return 1

set @ParentId=Scope_Identity( )

select @ParentId ParentId

return 0
Example 6-11. Stored procedure: SP0606_UpdateParent
CREATE PROCEDURE SP0606_UpdateParent
@ParentId int,
@Field1 nvarchar(50)=null,
@Field2 nvarchar(50)=null
AS
SET NOCOUNT ON

update
TBL0606Parent
set
Field1=@Field1,
Field2=@Field2
where
ParentId=@ParentId

if @@rowcount=0

return 1

return 0
Example 6-12. Stored procedure: SP0606_GetChild
CREATE PROCEDURE SP0606_GetChild
@ChildId int=null
AS
SET NOCOUNT ON

if @ChildId is not null
begin
select
ChildID,
ParentId,
Field3,
Field4
from
TBL0606Child
where
ChildId=@ChildId

return 0
end

select
ChildId,
ParentId,
Field3,
Field4
from

TBL0606Child

return 0
Example 6-13. Stored procedure: SP0606_DeleteChild
CREATE PROCEDURE SP0606_DeleteChild
@ChildId int
AS
SET NOCOUNT ON

delete
from
TBL0606Child
where
ChildId=@ChildId

return 0
Example 6-14. Stored procedure: SP0606_InsertChild
CREATE PROCEDURE SP0606_InsertChild
@ChildId int output,
@ParentId int,
@Field3 nvarchar(50)=null,
@Field4 nvarchar(50)=null
AS
SET NOCOUNT ON

insert TBL0606Child(
ParentId,
Field3,
Field4)
values (

@ParentId,
@Field3,
@Field4)

if @@rowcount=0
return 1

set @ChildId=Scope_Identity( )

select @ChildId ChildId

return 0
Example 6-15. Stored procedure: SP0606_UpdateChild
CREATE PROCEDURE SP0606_UpdateChild
@ChildId int,
@ParentId int,
@Field3 nvarchar(50)=null,
@Field4 nvarchar(50)=null
AS
SET NOCOUNT ON

update
TBL0606Child
set
ParentId=@ParentId,
Field3=@Field3,
Field4=@Field4
where
ChildId=@ChildId

if @@rowcount=0
return 1

return 0
Example 6-16. Stored procedure: SP0606_GetGrandchild
CREATE PROCEDURE SP0606_GetGrandchild
@GrandchildId int=null
AS
SET NOCOUNT ON

if @GrandchildId is not null
begin
select
GrandchildID,
ChildId,
Field5,
Field6
from
TBL0606Grandchild
where
GrandchildId=@GrandchildId

return 0
end

select
GrandchildId,
ChildId,
Field5,
Field6

from
TBL0606Grandchild

return 0
Example 6-17. Stored procedure: SP0606_DeleteGrandchild
CREATE PROCEDURE SP0606_DeleteGrandchild
@GrandchildId int
AS
SET NOCOUNT ON

delete
from
TBL0606Grandchild
where
GrandchildId=@GrandchildId

return 0
Example 6-18. Stored procedure: SP0606_InsertGrandchild
CREATE PROCEDURE SP0606_InsertGrandchild
@GrandchildId int output,
@ChildId int,
@Field5 nvarchar(50)=null,
@Field6 nvarchar(50)=null
AS
SET NOCOUNT ON

insert TBL0606Grandchild(
ChildId,
Field5,
Field6)

values (
@ChildId,
@Field5,
@Field6)

if @@rowcount=0
return 1

set @GrandchildId=Scope_Identity( )

select @GrandchildId GrandchildId

return 0
Example 6-19. Stored procedure: SP0606_UpdateGrandchild
CREATE PROCEDURE SP0606_UpdateGrandchild
@GrandchildId int,
@ChildId int,
@Field5 nvarchar(50)=null,
@Field6 nvarchar(50)=null
AS
SET NOCOUNT ON

update
TBL0606Grandchild
set
ChildId=@ChildId,
Field5=@Field5,
Field6=@Field6
where
GrandchildId=@GrandchildId

if @@rowcount=0
return 1

return 0
The C# code is shown in Example 6-20
.
Example 6-20. File: ReferentialIntegrityUpdateLogicForm.cs
// Namespaces, variables, and constants
using System;
using System.Configuration;
using System.Windows.Forms;
using System.Data;
using System.Data.SqlClient;

private DataSet ds;
private SqlDataAdapter daParent, daChild, daGrandchild;

private const String PARENTTABLENAME = "TBL00606Parent";
private const String CHILDTABLENAME = "TBL00606Child";
private const String GRANDCHILDTABLENAME = "TBL00606Grandchild";

// Table column name constants for Parent table
private const String PARENTID_FIELD = "ParentId";
private const String FIELD1_FIELD = "Field1";
private const String FIELD2_FIELD = "Field2";

// Table column parameter name constants for Child table
private const String CHILDID_FIELD = "ChildId";
private const String FIELD3_FIELD = "Field3";

private const String FIELD4_FIELD = "Field4";

// Table column parameter name constants for Grandchild table
private const String GRANDCHILDID_FIELD = "GrandchildId";
private const String FIELD5_FIELD = "Field5";
private const String FIELD6_FIELD = "Field6";

// Stored procedure name constants
private const String DELETEPARENT_SP = "SP0606_DeleteParent";
private const String GETPARENT_SP = "SP0606_GetParent";
private const String INSERTPARENT_SP = "SP0606_InsertParent";
private const String UPDATEPARENT_SP = "SP0606_UpdateParent";
private const String DELETECHILD_SP = "SP0606_DeleteChild";
private const String GETCHILD_SP = "SP0606_GetChild";
private const String INSERTCHILD_SP = "SP0606_InsertChild";
private const String UPDATECHILD_SP = "SP0606_UpdateChild";
private const String DELETEGRANDCHILD_SP = "SP0606_DeleteGrandchild";
private const String GETGRANDCHILD_SP = "SP0606_GetGrandchild";
private const String INSERTGRANDCHILD_SP = "SP0606_InsertGrandchild";
private const String UPDATEGRANDCHILD_SP = "SP0606_UpdateGrandchild";

// Stored procedure parameter name constants for Parent table
private const String PARENTID_PARM = "@ParentId";
private const String FIELD1_PARM = "@Field1";
private const String FIELD2_PARM = "@Field2";

// Stored procedure parameter name constants for Child table
private const String CHILDID_PARM = "@ChildId";
private const String FIELD3_PARM = "@Field3";
private const String FIELD4_PARM = "@Field4";

// Stored procedure parameter name constants for Child table
private const String GRANDCHILDID_PARM = "@GrandchildId";
private const String FIELD5_PARM = "@Field5";
private const String FIELD6_PARM = "@Field6";

// . . .

private void ReferentialIntegrityUpdateLogicForm_Load(object sender,
System.EventArgs e)
{
DataColumnCollection cols;
DataColumn col;

// Build the parent table.
DataTable parentTable = new DataTable(PARENTTABLENAME);
cols = parentTable.Columns;
col = cols.Add(PARENTID_FIELD, typeof(Int32));
col.AutoIncrement = true;
col.AutoIncrementSeed = -1;
col.AutoIncrementStep = -1;
cols.Add(FIELD1_FIELD, typeof(String)).MaxLength = 50;
cols.Add(FIELD2_FIELD, typeof(String)).MaxLength = 50;

// Build the child table.
DataTable childTable = new DataTable(CHILDTABLENAME);
cols = childTable.Columns;
col = cols.Add(CHILDID_FIELD, typeof(Int32));
col.AutoIncrement = true;
col.AutoIncrementSeed = -1;

col.AutoIncrementStep = -1;
cols.Add(PARENTID_FIELD, typeof(Int32)).AllowDBNull = false;
cols.Add(FIELD3_FIELD, typeof(String)).MaxLength = 50;
cols.Add(FIELD4_FIELD, typeof(String)).MaxLength = 50;

// Build the grandchild table.
DataTable grandchildTable = new DataTable(GRANDCHILDTABLENAME);
cols = grandchildTable.Columns;
col = cols.Add(GRANDCHILDID_FIELD, typeof(Int32));
col.AutoIncrement = true;
col.AutoIncrementSeed = -1;
col.AutoIncrementStep = -1;
cols.Add(CHILDID_FIELD, typeof(Int32)).AllowDBNull = false;
cols.Add(FIELD5_FIELD, typeof(String)).MaxLength = 50;
cols.Add(FIELD6_FIELD, typeof(String)).MaxLength = 50;

// Add the tables to the DataSet and create the relation between them.
ds = new DataSet( );
ds.Tables.Add(parentTable);
ds.Tables.Add(childTable);
ds.Tables.Add(grandchildTable);
ds.Relations.Add(new DataRelation("Parent_Child_Relation",
parentTable.Columns[PARENTID_FIELD],
childTable.Columns[PARENTID_FIELD], true));
ds.Relations.Add(new DataRelation("Child_Grandchild_Relation",
childTable.Columns[CHILDID_FIELD],
grandchildTable.Columns[CHILDID_FIELD], true));

// Create the DataAdapter objects for the tables.
daParent = new SqlDataAdapter( );

daChild = new SqlDataAdapter( );
daGrandchild = new SqlDataAdapter( );

// Build the parent select command.
SqlCommand selectCommand = new SqlCommand(GETPARENT_SP,
new SqlConnection(
ConfigurationSettings.AppSettings["Sql_ConnectString"]));
selectCommand.CommandType = CommandType.StoredProcedure;
daParent.SelectCommand = selectCommand;

// Build the parent delete command.
SqlCommand deleteCommand = new SqlCommand(DELETEPARENT_SP,
daParent.SelectCommand.Connection);
deleteCommand.CommandType = CommandType.StoredProcedure;
deleteCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0,
PARENTID_FIELD);
daParent.DeleteCommand = deleteCommand;

// Build the parent insert command.
SqlCommand insertCommand = new SqlCommand(INSERTPARENT_SP,
daParent.SelectCommand.Connection);
insertCommand.CommandType = CommandType.StoredProcedure;
insertCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0,
PARENTID_FIELD);
insertCommand.Parameters.Add(FIELD1_PARM, SqlDbType.NVarChar, 50,
FIELD1_FIELD);
insertCommand.Parameters.Add(FIELD2_PARM, SqlDbType.NVarChar, 50,
FIELD2_FIELD);
daParent.InsertCommand = insertCommand;

// Build the parent update command.
SqlCommand updateCommand = new SqlCommand(UPDATEPARENT_SP,
daParent.SelectCommand.Connection);
updateCommand.CommandType = CommandType.StoredProcedure;
updateCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0,
PARENTID_FIELD);
updateCommand.Parameters.Add(FIELD1_PARM, SqlDbType.NVarChar, 50,
FIELD1_FIELD);
updateCommand.Parameters.Add(FIELD2_PARM, SqlDbType.NVarChar, 50,
FIELD2_FIELD);
daParent.UpdateCommand = updateCommand;

// Build the child select command.
selectCommand = new SqlCommand(GETCHILD_SP,
new SqlConnection(
ConfigurationSettings.AppSettings["Sql_ConnectString"]));
selectCommand.CommandType = CommandType.StoredProcedure;
daChild.SelectCommand = selectCommand;

// Build the child delete command.
deleteCommand = new SqlCommand(DELETECHILD_SP,
daChild.SelectCommand.Connection);
deleteCommand.CommandType = CommandType.StoredProcedure;
deleteCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,
CHILDID_FIELD);
daChild.DeleteCommand = deleteCommand;

// Build the child insert command.
insertCommand = new SqlCommand(INSERTCHILD_SP,
daChild.SelectCommand.Connection);

insertCommand.CommandType = CommandType.StoredProcedure;
insertCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,
CHILDID_FIELD);
insertCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0,
PARENTID_FIELD);
insertCommand.Parameters.Add(FIELD3_PARM, SqlDbType.NVarChar, 50,
FIELD3_FIELD);
insertCommand.Parameters.Add(FIELD4_PARM, SqlDbType.NVarChar, 50,
FIELD4_FIELD);
daChild.InsertCommand = insertCommand;

// Build the child update command.
updateCommand = new SqlCommand(UPDATECHILD_SP,
daChild.SelectCommand.Connection);
updateCommand.CommandType = CommandType.StoredProcedure;
updateCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,
CHILDID_FIELD);
updateCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0,
PARENTID_FIELD);
updateCommand.Parameters.Add(FIELD3_PARM, SqlDbType.NVarChar, 50,
FIELD3_FIELD);
updateCommand.Parameters.Add(FIELD4_PARM, SqlDbType.NVarChar, 50,
FIELD4_FIELD);
daChild.UpdateCommand = updateCommand;

// Build the grandchild select command.
selectCommand = new SqlCommand(GETGRANDCHILD_SP,
new SqlConnection(
ConfigurationSettings.AppSettings["Sql_ConnectString"]));
selectCommand.CommandType = CommandType.StoredProcedure;

daGrandchild.SelectCommand = selectCommand;

// Build the grandchild delete command.
deleteCommand = new SqlCommand(DELETEGRANDCHILD_SP,
daGrandchild.SelectCommand.Connection);
deleteCommand.CommandType = CommandType.StoredProcedure;
deleteCommand.Parameters.Add(GRANDCHILDID_PARM, SqlDbType.Int, 0,
GRANDCHILDID_FIELD);
daGrandchild.DeleteCommand = deleteCommand;

// Build the grandchild insert command.
insertCommand = new SqlCommand(INSERTGRANDCHILD_SP,
daGrandchild.SelectCommand.Connection);
insertCommand.CommandType = CommandType.StoredProcedure;
insertCommand.Parameters.Add(GRANDCHILDID_PARM, SqlDbType.Int, 0,
GRANDCHILDID_FIELD);
insertCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,
CHILDID_FIELD);
insertCommand.Parameters.Add(FIELD5_PARM, SqlDbType.NVarChar, 50,
FIELD5_FIELD);
insertCommand.Parameters.Add(FIELD6_PARM, SqlDbType.NVarChar, 50,
FIELD6_FIELD);
daGrandchild.InsertCommand = insertCommand;

// Build the grandchild update command.
updateCommand = new SqlCommand(UPDATEGRANDCHILD_SP,
daGrandchild.SelectCommand.Connection);
updateCommand.CommandType = CommandType.StoredProcedure;
updateCommand.Parameters.Add(GRANDCHILDID_PARM, SqlDbType.Int, 0,
GRANDCHILDID_FIELD);

updateCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,
CHILDID_FIELD);
updateCommand.Parameters.Add(FIELD5_PARM, SqlDbType.NVarChar, 50,
FIELD5_FIELD);
updateCommand.Parameters.Add(FIELD6_PARM, SqlDbType.NVarChar, 50,
FIELD6_FIELD);
daGrandchild.UpdateCommand = updateCommand;

// Fill the parent and child table.
daParent.Fill(parentTable);
daChild.Fill(childTable);
daGrandchild.Fill(grandchildTable);

// Bind the default view of the data source to the grid.
dataGrid.DataSource = parentTable.DefaultView;

}

private void CreateData(int parentRows, int childRows, int grandchildRows)
{
// Generate some data into each of the related tables.
for(int iParent = 0; iParent < parentRows; iParent++)
{
// Generate parentRows of data in the parent table.
DataRow parentRow = ds.Tables[PARENTTABLENAME].NewRow( );
parentRow[FIELD1_FIELD] = Guid.NewGuid().ToString( );
parentRow[FIELD2_FIELD] = Guid.NewGuid().ToString( );
ds.Tables[PARENTTABLENAME].Rows.Add(parentRow);

for(int iChild = 0; iChild < childRows; iChild++)

{
// Generate childRows of data in the child table.
DataRow childRow = ds.Tables[CHILDTABLENAME].NewRow( );
childRow[PARENTID_FIELD] =
(int)parentRow[PARENTID_FIELD];
childRow[FIELD3_FIELD] = Guid.NewGuid().ToString( );
childRow[FIELD4_FIELD] = Guid.NewGuid().ToString( );
ds.Tables[CHILDTABLENAME].Rows.Add(childRow);

for(int iGrandchild = 0; iGrandchild < grandchildRows;
iGrandchild++)
{
// Generate grandchildRows of data in the
// grandchild table.
DataRow grandchildRow =
ds.Tables[GRANDCHILDTABLENAME].NewRow( );
grandchildRow[CHILDID_FIELD] =
(int)childRow[CHILDID_FIELD];
grandchildRow[FIELD5_FIELD] =
Guid.NewGuid().ToString( );
grandchildRow[FIELD6_FIELD] =
Guid.NewGuid().ToString( );
ds.Tables[GRANDCHILDTABLENAME].Rows.Add(
grandchildRow);
}
}
}
}

private void UpdateData( )

{
// Update the related tables.
daGrandchild.Update(ds.Tables[GRANDCHILDTABLENAME].Select(null, null,
DataViewRowState.Deleted));
daChild.Update(ds.Tables[CHILDTABLENAME].Select(null, null,
DataViewRowState.Deleted));
daParent.Update(ds.Tables[PARENTTABLENAME].Select(null, null,
DataViewRowState.Deleted));
daParent.Update(ds.Tables[PARENTTABLENAME].Select(null, null,
DataViewRowState.ModifiedCurrent));
daParent.Update(ds.Tables[PARENTTABLENAME].Select(null, null,
DataViewRowState.Added));
daChild.Update(ds.Tables[CHILDTABLENAME].Select(null, null,
DataViewRowState.ModifiedCurrent));
daChild.Update(ds.Tables[CHILDTABLENAME].Select(null, null,
DataViewRowState.Added));
daGrandchild.Update(ds.Tables[GRANDCHILDTABLENAME].Select(null, null,
DataViewRowState.ModifiedCurrent));
daGrandchild.Update(ds.Tables[GRANDCHILDTABLENAME].Select(null, null,
DataViewRowState.Added));
}

private void createDataButton_Click(object sender, System.EventArgs e)
{
// Create four rows of data in each parent, child, and grandchild.
CreateData(4, 4, 4);
// Update the data source with the new data.
UpdateData( );

MessageBox.Show("Data created.", "Referential Integrity",

MessageBoxButtons.OK, MessageBoxIcon.Information);
}

private void modifyButton_Click(object sender, System.EventArgs e)
{
// Randomly delete or modify rows from the grandchild, child, and
// parent rows.
Random r = new Random((int)DateTime.Now.Ticks);

// Modify grandchild rows.
for(int i = ds.Tables[GRANDCHILDTABLENAME].Rows.Count; i > 0; i )
{
DataRow grandchildRow =
ds.Tables[GRANDCHILDTABLENAME].Rows[i - 1];

if(r.Next(2) == 0)
{
grandchildRow[FIELD5_FIELD] = Guid.NewGuid().ToString( );
grandchildRow[FIELD6_FIELD] = Guid.NewGuid().ToString( );
}
else
grandchildRow.Delete( );
}

// Modify or delete child rows.
for(int i = ds.Tables[CHILDTABLENAME].Rows.Count; i > 0; i )
{
DataRow childRow = ds.Tables[CHILDTABLENAME].Rows[i - 1];

if(r.Next(2) == 0)

{
childRow[FIELD3_FIELD] = Guid.NewGuid().ToString( );
childRow[FIELD4_FIELD] = Guid.NewGuid().ToString( );
}
else
childRow.Delete( );
}

// Modify or delete parent rows.
for(int i = ds.Tables[PARENTTABLENAME].Rows.Count; i > 0; i )
{
DataRow parentRow = ds.Tables[PARENTTABLENAME].Rows[i - 1];

if(r.Next(2) == 0)
{
parentRow[FIELD1_FIELD] = Guid.NewGuid().ToString( );
parentRow[FIELD2_FIELD] = Guid.NewGuid().ToString( );
}
else
parentRow.Delete( );

}

// Insert two rows into parent, child, and grandchild.
CreateData(2 ,2, 2);

// Update the data source with the changes.
UpdateData( );

MessageBox.Show("Data randomly modified.", "Referential Integrity",

MessageBoxButtons.OK, MessageBoxIcon.Information);
}

private void deleteButton_Click(object sender, System.EventArgs e)
{
// Delete the parent data which cascades by default
// to child and grandchild records.
for(int i = ds.Tables[PARENTTABLENAME].Rows.Count; i > 0; i )
ds.Tables[PARENTTABLENAME].Rows[i - 1].Delete( );

// Update the data source with the changes.
UpdateData( );

MessageBox.Show("Data deleted.", "Referential Integrity",
MessageBoxButtons.OK, MessageBoxIcon.Information);
}
Discussion
To avoid referential integrity problems when updating the data source from a DataSet
containing related tables, use one DataAdapter for each DataTable to update the deleted,
updated, and inserted rows in the following order:
1. Deleted grandchild rows
2. Deleted child rows
3. Deleted parent rows
4. Updated parent rows
5. Inserted parent rows
6. Updated child rows
7. Inserted child rows
8. Updated grandchild rows
9. Inserted grandchild rows
In the solution, this is done using the following code:

daGrandchild.Update(ds.Tables[GRANDCHILDTABLENAME].Select(null, null,
DataViewRowState.Deleted));
daChild.Update(ds.Tables[CHILDTABLENAME].Select(null, null,
DataViewRowState.Deleted));
daParent.Update(ds.Tables[PARENTTABLENAME].Select(null, null,
DataViewRowState.Deleted));
daParent.Update(ds.Tables[PARENTTABLENAME].Select(null, null,
DataViewRowState.ModifiedCurrent));
daParent.Update(ds.Tables[PARENTTABLENAME].Select(null, null,
DataViewRowState.Added));
daChild.Update(ds.Tables[CHILDTABLENAME].Select(null, null,
DataViewRowState.ModifiedCurrent));
daChild.Update(ds.Tables[CHILDTABLENAME].Select(null, null,
DataViewRowState.Added));
daGrandchild.Update(ds.Tables[GRANDCHILDTABLENAME].Select(null, null,
DataViewRowState.ModifiedCurrent));
daGrandchild.Update(ds.Tables[GRANDCHILDTABLENAME].Select(null, null,
DataViewRowState.Added));
There are three related tables—parent, child, and grandparent—and one DataAdapter for
each table. An overload of the Select( ) method of the DataTable is used to retrieve the
subset of rows identified by the state argument containing a value from the
DataViewRowState enumeration:
• Added to get the subset of inserted rows
• Deleted to get the subset of deleted rows
• ModifiedCurrent to get the subset of modified rows
There are few other considerations involving the primary key:
• If the primary key cannot be modified once added, the updated and inserted rows
can be processed together in the same statement.
• If the primary key can be modified after it has been added, the database must
cascade the updated primary key values to the child records or else a referential

integrity violation will occur. The UpdateCommand property of child tables must
accept either the Original or the Current value of the foreign key if it is used in the
concurrency check.
• If the primary key for the DataTable is an auto-increment value and the primary
key value is generated by the data source, the InsertCommand must return the
primary key value from the data source and use it to update the value in the
DataSet. The DataSet can automatically cascade this new value to the foreign keys
in the related child records.
[ Team LiB ]