关于DataRow的RowState和RowVersion

关于DataRow的RowState和RowVersion

1）什么是DataRow's RowState and RowVersion？
      DataRow's RowState是数据行的状态，RowVersion是数据行的版本。
   RowState and Row Version are both enum object.
   The codesnap is the following detail:

DataRowState
[Flags]
public enum DataRowState
{
    Added = 4,
    Deleted = 8,
    Detached = 1,
    Modified = 0x10,
    Unchanged = 2
}

 

RowVersion
public enum DataRowVersion
{
    Current = 0x200,
    Default = 0x600,
    Original = 0x100,
    Proposed = 0x400
}

 

 

2) 究竟RowState和RowVersion有什么关系呢？又个有什么用途呢？
  RowState和RowVersion有一个对照关系(或许描述有点不恰当),
  关系如下所示: 

RowState	RowVersion
Added	Current(Default)
Modified	Current(Default)
	Original
Unchanged	Current(Default)
	Original(Default)
Detached	Proposed(Default)
Deleted	Original (Default)

For unchanged rowstate, default row version is also Proposed,从下面的例子中，你能看到。
从上面的表格可以看出，一个数据行有版本的控制，为什么要有这版本控制呢？
A)用于DataSet和DataTable内部实现，
B)
在用DataAdapter跟DB交互时(Call Update(DataSet))，用什么版本赋值。
当然只是在DBParameter上设置SourceVersion

DataAdapter
public interface IDataAdapter
{
    // Methods
    int Fill(DataSet dataSet);
    DataTable[] FillSchema(DataSet dataSet, SchemaType schemaType);
    IDataParameter[] GetFillParameters();
    int Update(DataSet dataSet);

    // Properties
    MissingMappingAction MissingMappingAction { get; set; }
    MissingSchemaAction MissingSchemaAction { get; set; }
    ITableMappingCollection TableMappings { get; }
}

 

 

DBParameter
public interface IDataParameter
{
    // Properties
    DbType DbType { get; set; }
    ParameterDirection Direction { get; set; }
    bool IsNullable { get; }
    string ParameterName { get; set; }
    string SourceColumn { get; set; }
    DataRowVersion SourceVersion { get; set; }
    object Value { get; set; }
}

 

3) 在DataTable.Select()和DataView.RowStateFilter区别,

public DataRow[] Select (
string filterExpression,
string sort,
DataViewRowState recordStates
)

Select

public Select(DataTable table, string filterExpression, string sort, DataViewRowState recordStates)

{

    this.table = table;

    this.IndexFields = table.ParseSortString(sort);

    this.indexDesc = ConvertIndexFieldtoIndexDesc(this.IndexFields);

    if ((filterExpression != null) && (filterExpression.Length > 0))

    {

        this.rowFilter = new DataExpression(this.table, filterExpression);

        this.expression = this.rowFilter.ExpressionNode;

    }

    this.recordStates = recordStates;

}



 

public Object this [
DataColumn column,
DataRowVersion version
] { get; }

public DataViewRowState RowStateFilter { get; set; }

其实在性能方面，DataView比DataTable好，DataView use index.

还是回到这个主题上吧，

DataTable的方法会返回所有的版本的数据行，而DataView仅返回相关的版本。

请看下面的例子：

 
Example

using System;

using System.Collections.Generic;

using System.Text;

using System.Data;



namespace DataRowEx

{

    class Program

    {

        static void Main(string[] args)

        {

            TestRowStateAndRowVersion();

        }



        private static void TestRowStateAndRowVersion()

        {

            DataTable customerTable = new DataTable("Customers");

            // Add columns

            customerTable.Columns.Add("id", typeof(int));

            customerTable.Columns.Add("name", typeof(string));



            // Set PrimaryKey

            customerTable.Columns["id"].Unique = true;

            customerTable.PrimaryKey = new DataColumn[] { customerTable.Columns["id"] };



            // Add ten rows

            for (int id = 1; id <= 3; id++)

            {

                customerTable.Rows.Add(

                    new object[] { customerTable.Rows.Count, string.Format("customer{0}", customerTable.Rows.Count) });

            }

            customerTable.AcceptChanges();



            // Change one row's value:

            customerTable.Rows[0].BeginEdit();

            customerTable.Rows[0]["name"] = "customer Modified";

    

            // Add one row:

           DataRow dataRow = customerTable.NewRow();

           dataRow["id"] = customerTable.Rows.Count;

           dataRow["name"] = "customer Added";

           customerTable.Rows.Add(dataRow);



           // Add one row:

           dataRow = customerTable.NewRow();

           dataRow["id"] = customerTable.Rows.Count;

           dataRow["name"] = "customer proposed";



            // Delete three rows.

            customerTable.Rows[1].Delete();

            customerTable.Rows[2].Delete();

            customerTable.Rows[3].Delete();



 

            // Use the Select method to find all rows matching the filter.

            DataRow[] foundRows =

                customerTable.Select(string.Empty, string.Empty,

                DataViewRowState.OriginalRows);



            PrintRows(foundRows, "filtered rows by originalRows");



            // Create a DataView with the table.

            DataView dataView = new DataView(customerTable);



            // Set the RowStateFilter to display only added and modified rows.

            dataView.RowStateFilter = DataViewRowState.Added

                | DataViewRowState.ModifiedCurrent;



            // Print those rows. Output = "Hello" "World";

            PrintView(dataView, "ModifiedCurrent and Added");



            // Set filter to display on originals of modified rows.

            dataView.RowStateFilter = DataViewRowState.ModifiedOriginal;

            PrintView(dataView, "ModifiedOriginal");





            // Set the RowStateFilter to display only Added and modified rows.

            dataView.RowStateFilter = DataViewRowState.Deleted;

            PrintView(dataView, "Deleted");



            //Set filter to display only current.

            dataView.RowStateFilter = DataViewRowState.CurrentRows;

            PrintView(dataView, "Current");



            // Set filter to display only unchanged rows.

            dataView.RowStateFilter = DataViewRowState.Unchanged;

            PrintView(dataView, "Unchanged");



            // Set filter to display only original rows.

            dataView.RowStateFilter = DataViewRowState.OriginalRows;

            PrintView(dataView, "OriginalRows");



            dataView.RowStateFilter = DataViewRowState.None;

            PrintView(dataView, "None");



        }



        private static void PrintRows(DataRow[] rows, string label)

        {

            Console.WriteLine("\n{0}", label);

            if (rows.Length <= 0)

            {

                Console.WriteLine("no rows found");

                return;

            }



            foreach (DataRow row in rows)

            {

                Console.WriteLine("Row State is {0};", row.RowState);

                Console.WriteLine("Current Version is {0};", row.HasVersion(DataRowVersion.Current));

                Console.WriteLine("Original Version is {0};", row.HasVersion(DataRowVersion.Original));

                Console.WriteLine("Proposed Version is {0};", row.HasVersion(DataRowVersion.Proposed));



                if (row.RowState == DataRowState.Deleted) continue;

                foreach (DataColumn column in row.Table.Columns)

                {

                    Console.Write("({0}) ", row[column,DataRowVersion.Default]);

                }

                Console.WriteLine();

            }

        }



        static private void PrintView(DataView dataView, string label)

        {

            Console.WriteLine("\n" + label);

            for (int i = 0; i < dataView.Count; i++)

            {

                Console.Write("Version is {0} -----", Enum.GetName(typeof(DataRowVersion),dataView[i].RowVersion));

                Console.WriteLine(dataView[i]["name"]);

            }

        }

    }

}




当直接访问删除的数据时，要用databview，否则会出错：

Deleted row information cannot be accessed through the row.

dataView[i].Row[1,DataRowVersion.Original]

dataView[i]["name"]

也不能用dataView[i].Row[1,DataRowVersion.Default]，

对于Unchanged's RowState,如果Call BeginEdit(),没有call EndEdit(),

运行上面的例子，就知道答案了。

(4)在ADO.NET 2.0中，DatRow添加了几个新的方法：

SetAdded()and SetModified()