/// --------------------------------------------------------------------------------
/// <summary>
/// Locks the database record associated with this object by selecting and locking
/// the row in the database. Supported in Microsoft SQLServer, Pervasive and MySQL.
/// The record lock is released when the transaction is committed or rolled back.
/// Throws an exception if not in transaction mode.
/// Returns the field values from the record that has been locked.
/// </summary>
/// --------------------------------------------------------------------------------
public SQL.SQLFieldValues ObjectLockRecord(IDatabaseObjects objCollection, IDatabaseObject objItem)
{
SQL.SQLSelect objSelect = new SQL.SQLSelect();
SQL.SQLConditions objSubset;
objSelect.PerformLocking = true;
objSelect.Tables.Add(objCollection.TableName());
objSelect.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objItem.DistinctValue);
objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objSelect.Where.Add(objSubset);
using (var objReader = this.Transactions.Execute(objSelect))
{
if (objReader.Read())
return FieldValuesFromDataReader(objCollection, objReader);
else
throw new Exceptions.ObjectDoesNotExistException(objCollection, objItem.DistinctValue);
}
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Extracts the fields to save to the database from the objItem.SaveFields function.
/// The fields are then written to the database using either an SQL INSERT or UPDATE
/// depending on whether the object has already been saved. If the collection has
/// implemented IDatabaseObjects.KeyFieldName then objItem's key is also validated to
/// ensure it is not null and unique within the collection. If objCollection has
/// implemented IDatabaseObjects.Subset then objItem should exist within objCollection.
/// If not, a duplicate key error may occur if the obItem's key is being used in
/// another subset in the same table. If a record is being amended
/// (IDatabaseObject.IsSaved returns true) then the function will "AND" the collection's
/// IDatabaseObjects.Subset conditions and the objItem's IDatabaseObject.DistinctValue
/// value to create the WHERE clause in the UPDATE statement. Therefore, the
/// combination of the IDatabaseObjects.Subset and IDatabaseObject.DistinctValue
/// conditions MUST identify only one record in the table. Otherwise multiple records
/// will be updated with the same data. If data is only inserted and not amended
/// (usually a rare occurance) then this requirement is unnecessary.
/// </summary>
///
/// <param name="objCollection">
/// The collection which contains or will contain the object to save.
/// </param>
///
/// <param name="objItem">
/// The object to save to the database. The values saved to the database are extracted from the
/// SQLFieldValues object returned from IDatabaseObject.SaveFields.
/// </param>
///
/// <example> Saves a product object (Me) to the database.
/// <code>
/// Public Sub Save()
///
/// objDatabase.ObjectSave(NorthwindDB.Products, Me)
///
/// End Sub
/// </code>
/// </example>
/// --------------------------------------------------------------------------------
///
public void ObjectSave(IDatabaseObjects objCollection, IDatabaseObject objItem)
{
SQL.SQLFieldValues objFieldValues;
var objNewGUID = Guid.Empty;
var autoAssignment = MergeDistinctFieldAutoAssignmentAndDistinctFieldAutoIncrements(objCollection);
objFieldValues = objItem.SaveFields();
if (objFieldValues == null)
throw new Exceptions.DatabaseObjectsException(objItem.GetType().Name + " IDatabaseObject.SaveFields not implemented");
//Add the distinct field value if it hasn't been added via the SaveFields sub
if (!objFieldValues.Exists(objCollection.DistinctFieldName()))
{
if (autoAssignment == SQL.FieldValueAutoAssignmentType.None)
objFieldValues.Add(objCollection.DistinctFieldName(), objItem.DistinctValue);
else if (autoAssignment == SQL.FieldValueAutoAssignmentType.NewUniqueIdentifier)
{
//For a new object, with a GUID that should be automatically assigned
//Create a new GUID for the distinct field so that it saved for the INSERT
if (!objItem.IsSaved)
{
objNewGUID = System.Guid.NewGuid();
objFieldValues.Add(objCollection.DistinctFieldName(), objNewGUID);
}
}
}
#if !DEBUG
ItemKeyEnsureValid(objCollection, objItem, objFieldValues);
#endif
using (ConnectionScope objConnection = new ConnectionScope(this))
{
if (objItem.IsSaved)
{
var objUpdate = new SQL.SQLUpdate();
objUpdate.TableName = objCollection.TableName();
objUpdate.Fields.Add(objFieldValues);
objUpdate.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objItem.DistinctValue);
var objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
{
objUpdate.Where.Add(objSubset);
}
if (objConnection.ExecuteNonQuery(objUpdate) != 1)
throw new Exceptions.RecordDoesNotExistException(objCollection, objItem);
}
else
{
var objInsert = new SQL.SQLInsert();
objInsert.TableName = objCollection.TableName();
objInsert.Fields = objFieldValues;
objConnection.ExecuteNonQuery(objInsert);
if (autoAssignment == SQL.FieldValueAutoAssignmentType.NewUniqueIdentifier)
objItem.DistinctValue = objNewGUID;
else if (autoAssignment == SQL.FieldValueAutoAssignmentType.AutoIncrement)
objItem.DistinctValue = objConnection.ExecuteScalar(new SQL.SQLAutoIncrementValue());
object objRollbackDistinctValue = objItem.DistinctValue;
objItem.IsSaved = true;
if (Transaction.Current != null)
{
Transaction.Current.EnlistVolatile(new TransactionExecuteActionOnRollback(() => objItem.IsSaved = false), EnlistmentOptions.None);
Transaction.Current.EnlistVolatile(new TransactionExecuteActionOnRollback(() => objItem.DistinctValue = objRollbackDistinctValue), EnlistmentOptions.None);
}
}
}
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Returns whether an object exists for the specified distinct value in the collection.
/// </summary>
///
/// <param name="objCollection">
/// The collection that is searched for the distinct value.
/// </param>
///
/// <param name="objDistinctValue">
/// The value to search for in the collection. This is the value of the field defined
/// by the collection's IDatabaseObjects.DistinctFieldName function.
/// </param>
/// --------------------------------------------------------------------------------
///
public bool ObjectExistsByDistinctValue(IDatabaseObjects objCollection, object objDistinctValue)
{
SQL.SQLSelect objSelect = new SQL.SQLSelect();
SQL.SQLConditions objSubset;
objSelect.Tables.Add(objCollection.TableName());
objSelect.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objDistinctValue);
objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objSelect.Where.Add(objSubset);
using (ConnectionScope objConnection = new ConnectionScope(this))
using (IDataReader objReader = objConnection.Execute(objSelect))
return objReader.Read();
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Gets and returns the field value from the database record associated with the
/// object and collection.
/// </summary>
/// <param name="objCollection">
/// The collection that the object exists within.
/// The function utilises the collection's subset and tablename to determine which
/// table and record to read.
/// Returns DBNull.Value if the field is NULL.
/// </param>
/// <param name="objItem">
/// The object which represents the database record to be read. Specifically,
/// the object's distinct field name is used to determine which record to read.
/// </param>
/// <param name="strFieldName">
/// The name of the database field that is to be read.
/// </param>
/// <exception cref="Exceptions.ObjectDoesNotExistException">If the object has not already been saved.</exception>
/// --------------------------------------------------------------------------------
public object ObjectGetFieldValue(IDatabaseObjects objCollection, IDatabaseObject objItem, string strFieldName)
{
if (!objItem.IsSaved)
throw new Exceptions.ObjectDoesNotExistException(objItem);
SQL.SQLSelect objSelect = new SQL.SQLSelect();
SQL.SQLConditions objSubset;
objSelect.Fields.Add(strFieldName);
objSelect.Tables.Add(objCollection.TableName());
objSelect.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objItem.DistinctValue);
objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objSelect.Where.Add(objSubset);
using (ConnectionScope objConnection = new ConnectionScope(this))
{
using (IDataReader objReader = objConnection.Execute(objSelect))
{
if (objReader.Read())
return objReader[0];
else
throw new Exceptions.ObjectDoesNotExistException(objCollection, objItem.DistinctValue);
}
}
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Initializes an existing object with values from a set of database fields.
/// Specifically, sets the IDatbaseObject.IsSaved property to true,
/// sets the IDatbaseObject.DistinctValue using the provided data and
/// calls IDatbaseObject.LoadFields().
/// </summary>
///
/// <param name="objCollection">
/// The collection associated with the field values. This is not used
/// to create an object - but to set the distinct field for the object using the
/// IDatabaseObjects.DistinctFieldName property.
/// </param>
///
/// <param name="objFieldValues">
/// The data container that contains the data to be copied into the object.
/// </param>
/// --------------------------------------------------------------------------------
public static void ObjectLoad(IDatabaseObjects objCollection, IDatabaseObject objItem, SQL.SQLFieldValues objFieldValues)
{
if (objFieldValues == null)
throw new ArgumentNullException();
objItem.IsSaved = true;
objItem.DistinctValue = objFieldValues[objCollection.DistinctFieldName()].Value;
objItem.LoadFields(objFieldValues);
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Deletes an object's database record. If the collection's IDatabaseObjects.Subset
/// has been implemented then the object must exist within the subset, otherwise the
/// object will not be deleted. If the object has not been saved to the database the
/// function will exit without executing an SQL DELETE command. After deleting the
/// database record the object is set to Nothing. The calling function should receive
/// the object ByRef for this to have any affect. Setting the object to Nothing
/// minimises the possibility of the deleted object being used in code after
/// ObjectDelete has been called.
/// </summary>
///
/// <param name="objCollection">
/// The collection that contains the object to delete. If the item does not exist
/// within the collection then the object will not be deleted.
/// </param>
///
/// <param name="objItem">
/// The object to delete. The calling function should receive this object ByRef
/// as the object is set to Nothing after deletion.
/// Reference Type: <see cref="IDatabaseObject" /> (DatabaseObjects.IDatabaseObject)
/// </param>
///
/// <example>
/// <code>
/// Public Sub Delete(ByRef objProduct As Product)
///
/// objDatabase.ObjectDelete(Me, objProduct)
/// 'objProduct will now be Nothing
///
/// End Sub
/// </code>
/// </example>
/// --------------------------------------------------------------------------------
///
public void ObjectDelete(IDatabaseObjects objCollection, ref IDatabaseObject objItem)
{
if (objItem.IsSaved)
{
SQL.SQLDelete objDelete = new SQL.SQLDelete();
SQL.SQLConditions objSubset;
objDelete.TableName = objCollection.TableName();
objDelete.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objItem.DistinctValue);
objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objDelete.Where.Add(objSubset);
using (ConnectionScope objConnection = new ConnectionScope(this))
objConnection.ExecuteNonQuery(objDelete);
objItem.IsSaved = false;
if (Transaction.Current != null)
{
IDatabaseObject objItemCopy = objItem;
Transaction.Current.EnlistVolatile(new TransactionExecuteActionOnRollback(() => objItemCopy.IsSaved = true), EnlistmentOptions.None);
}
}
//The function that calls ObjectDelete objItem MUST be ByRef for this to have any effect
objItem = null;
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Returns the database fields for an object from the collection using a distinct value
/// (see IDatabaseObjects.DistinctFieldName).
/// Returns Nothing/null if the distinct value does not exist.
/// </summary>
/// --------------------------------------------------------------------------------
///
private SQL.SQLFieldValues ObjectFieldValuesIfExists(IDatabaseObjects objCollection, object objDistinctValue)
{
SQL.SQLSelect objSelect = new SQL.SQLSelect();
SQL.SQLConditions objSubset;
SQL.SQLSelectTable objPrimaryTable = objSelect.Tables.Add(objCollection.TableName());
objSelect.Tables.Joins = objCollection.TableJoins(objPrimaryTable, objSelect.Tables);
objSelect.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objDistinctValue);
objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objSelect.Where.Add(objSubset);
using (ConnectionScope objConnection = new ConnectionScope(this))
{
using (IDataReader objReader = objConnection.Execute(objSelect))
{
if (objReader.Read())
return FieldValuesFromDataReader(objCollection, objReader);
else
return null;
}
}
}
private IDictionary ObjectsDictionaryBase(IDatabaseObjects objCollection, bool bKeyIsDistinctField = false)
{
//Returns an IDictionary with the key being either the DistinctField or KeyField
IDictionary objDictionary = new Hashtable();
SQL.SQLSelect objSelect = new SQL.SQLSelect();
string strKeyField;
SQL.SQLSelectTable objPrimaryTable = objSelect.Tables.Add(objCollection.TableName());
objSelect.Tables.Joins = objCollection.TableJoins(objPrimaryTable, objSelect.Tables);
objSelect.Where = objCollection.Subset();
objSelect.OrderBy = objCollection.OrderBy();
using (ConnectionScope objConnection = new ConnectionScope(this))
{
using (IDataReader objReader = objConnection.Execute(objSelect))
{
if (bKeyIsDistinctField)
strKeyField = objCollection.DistinctFieldName();
else
strKeyField = objCollection.KeyFieldName();
while (objReader.Read())
objDictionary.Add(objReader[strKeyField], ObjectFromDataReader(objCollection, objReader));
return objDictionary;
}
}
}
private object ItemKeyFieldValue(IDatabaseObjects objCollection, IDatabaseObject objItem, SQL.SQLFieldValues objFieldValues)
{
//On the rare occurance that the KeyField is the same as the DistinctField
//then the key value may not have been set in the Save and therefore be
//available in the objFieldValues collection. In which case the
//key has to be extracted from the objItem.DistinctField.
object objKeyFieldValue;
if (string.Compare(objCollection.DistinctFieldName(), objCollection.KeyFieldName(), true) == 0)
objKeyFieldValue = objItem.DistinctValue;
else
objKeyFieldValue = objFieldValues[objCollection.KeyFieldName()].Value;
return objKeyFieldValue;
}
private void ItemKeyEnsureValid(IDatabaseObjects objCollection, IDatabaseObject objItem, SQL.SQLFieldValues objFieldValues)
{
SQL.SQLSelect objSelect;
object objKeyFieldValue;
SQL.SQLConditions objSubset;
//If the key field is set and the key field is specified in the object
if (objCollection.KeyFieldName() != string.Empty && objFieldValues.Exists(objCollection.KeyFieldName()))
{
objKeyFieldValue = ItemKeyFieldValue(objCollection, objItem, objFieldValues);
if (objKeyFieldValue is string)
{
if (String.IsNullOrEmpty((string)objKeyFieldValue))
throw new Exceptions.DatabaseObjectsException(objItem.GetType().Name + " " + objCollection.KeyFieldName() + " field is Null");
}
objSelect = new SQL.SQLSelect();
objSelect.Tables.Add(objCollection.TableName());
objSelect.Fields.Add(objCollection.KeyFieldName());
objSelect.Where.Add(objCollection.KeyFieldName(), SQL.ComparisonOperator.EqualTo, objKeyFieldValue);
objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objSelect.Where.Add(objSubset);
if (objItem.IsSaved)
objSelect.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.NotEqualTo, objItem.DistinctValue);
using (ConnectionScope objConnection = new ConnectionScope(this))
using (IDataReader objReader = objConnection.Execute(objSelect))
if (objReader.Read())
throw new Exceptions.ObjectAlreadyExistsException(objItem, objKeyFieldValue);
}
}
private static SQL.SQLFieldValues FieldValuesFromDataReader(IDatabaseObjects objCollection, IDataReader objReader)
{
string strFieldName;
string strTablePrefix;
SQL.SQLFieldValues objFieldValues;
//check that the distinct field name exists
if (!FieldExists(objReader, objCollection.DistinctFieldName()))
throw new Exceptions.DatabaseObjectsException(System.Convert.ToString(((object) objCollection).GetType().Name + ".DistinctFieldName '" + objCollection.DistinctFieldName() + "' is invalid"));
objFieldValues = new SQL.SQLFieldValues();
strTablePrefix = objCollection.TableName() + ".";
//Copy the recordset values into the SQL.SQLFieldValues object
for (int intIndex = 0; intIndex < objReader.FieldCount; intIndex++)
{
//If the recordset has been loaded with a join then it may be prefixed with
//the table name - this is the case with Microsoft Access
//If so remove the table name if the table prefix is the same as objCollection.TableName
//All of the other joined fields with tablename prefixes on the fields will remain. This is ok considering
//most of the time an inner join has been performed where the field names are equal in the 2 joined tables
strFieldName = objReader.GetName(intIndex);
if (strFieldName.IndexOf(strTablePrefix) == 0)
objFieldValues.Add(strFieldName.Substring(strTablePrefix.Length), objReader[intIndex]);
else
objFieldValues.Add(strFieldName, objReader[intIndex]);
}
return objFieldValues;
}
/// --------------------------------------------------------------------------------
/// <summary>
/// Sets the field value for the database record associated with the object and
/// collection.
/// </summary>
/// <param name="objCollection">
/// The collection that the object exists within.
/// The function utilises the collection's subset and tablename to determine which
/// table and record to modify.
/// </param>
/// <param name="objItem">
/// The object which represents the database record to be set. Specifically,
/// the object's distinct field name is used to determine which record to modify.
/// </param>
/// <param name="strFieldName">
/// The name of the database field that is to be set.
/// </param>
/// <param name="objNewValue">
/// The new value that the database field it to be set to.
/// If Nothing/null then the field is set to NULL.
/// </param>
/// <exception cref="Exceptions.ObjectDoesNotExistException">If the object has not already been saved</exception>
/// --------------------------------------------------------------------------------
public void ObjectSetFieldValue(IDatabaseObjects objCollection, IDatabaseObject objItem, string strFieldName, object objNewValue)
{
if (!objItem.IsSaved)
throw new Exceptions.ObjectDoesNotExistException(objItem);
SQL.SQLUpdate objUpdate = new SQL.SQLUpdate();
objUpdate.TableName = objCollection.TableName();
objUpdate.Fields.Add(strFieldName, objNewValue);
objUpdate.Where.Add(objCollection.DistinctFieldName(), SQL.ComparisonOperator.EqualTo, objItem.DistinctValue);
var objSubset = objCollection.Subset();
if (objSubset != null && !objSubset.IsEmpty)
objUpdate.Where.Add(objSubset);
using (ConnectionScope objConnection = new ConnectionScope(this))
objConnection.ExecuteNonQuery(objUpdate);
}
public ObjectAlreadyLockedException(IDatabaseObjects objCollection, IDatabaseObject objObject)
: base(objObject.GetType().Name + "." + objCollection.DistinctFieldName() + " " + objObject.DistinctValue.ToString() + " is already locked")
{
}
