asp.net DataTable相关操作集锦(筛选,取前N条数据,去重复行,获取指定列数据等)

#region DataTable筛选，排序返回符合条件行组成的新DataTable或直接用DefaultView按条件返回
/// <summary>
/// DataTable筛选，排序返回符合条件行组成的新DataTable或直接用DefaultView按条件返回
/// eg:SortExprDataTable(dt,"Sex='男'","Time Desc",1)
/// </summary>
/// <param name="dt">传入的DataTable</param>
/// <param name="strExpr">筛选条件</param>
/// <param name="strSort">排序条件</param>
/// <param name="mode">1,直接用DefaultView按条件返回,效率较高;2,DataTable筛选，排序返回符合条件行组成的新DataTable</param>
public static DataTable SortDataTable(DataTable dt, string strExpr, string strSort, int mode)
{
  switch (mode)
  {
    case 1:
      //方法一　直接用DefaultView按条件返回
      dt.DefaultView.RowFilter = strExpr;
      dt.DefaultView.Sort = strSort;
      return dt;
    case 2:
      //方法二　DataTable筛选，排序返回符合条件行组成的新DataTable
      DataTable dt1 = new DataTable();
      DataRow[] GetRows = dt.Select(strExpr, strSort);
      //复制DataTable dt结构不包含数据
      dt1 = dt.Clone();
      foreach (DataRow row in GetRows)
      {
        dt1.Rows.Add(row.ItemArray);
      }
      return dt1;
    default:
      return dt;
  }
}
#endregion

#region 获取DataTable前几条数据
/// <summary>
/// 获取DataTable前几条数据
/// </summary>
/// <param name="TopItem">前N条数据</param>
/// <param name="oDT">源DataTable</param>
/// <returns></returns>
public static DataTable DtSelectTop(int TopItem, DataTable oDT)
{
  if (oDT.Rows.Count < TopItem) return oDT;
  DataTable NewTable = oDT.Clone();
  DataRow[] rows = oDT.Select("1=1");
  for (int i = 0; i < TopItem; i++)
  {
    NewTable.ImportRow((DataRow)rows[i]);
  }
  return NewTable;
}
#endregion

#region 获取DataTable中指定列的数据
/// <summary>
/// 获取DataTable中指定列的数据
/// </summary>
/// <param name="dt">数据源</param>
/// <param name="tableName">新的DataTable的名词</param>
/// <param name="strColumns">指定的列名集合</param>
/// <returns>返回新的DataTable</returns>
public static DataTable GetTableColumn(DataTable dt, string tableName, params string[] strColumns)
{
  DataTable dtn = new DataTable();
  if (dt == null)
  {
    throw new ArgumentNullException("参数dt不能为null");
  }
  try
  {
    dtn = dt.DefaultView.ToTable(tableName, true, strColumns);
  }
  catch (Exception e)
  {
    throw new Exception(e.Message);
  }
  return dtn;
}
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using System.Collections;
using System.Text;
namespace GuanEasy
{
/// <summary>
/// DataSet助手
/// </summary>
public class DataSetHelper
{
private class FieldInfo
{
public string RelationName;
public string FieldName;
public string FieldAlias;
public string Aggregate;
}
private DataSet ds;
private ArrayList m_FieldInfo;
private string m_FieldList;
private ArrayList GroupByFieldInfo;
private string GroupByFieldList;
public DataSet DataSet
{
get { return ds; }
}
#region Construction
public DataSetHelper()
{
ds = null;
}
public DataSetHelper(ref DataSet dataSet)
{
ds = dataSet;
}
#endregion
#region Private Methods
private bool ColumnEqual(object objectA, object objectB)
{
if ( objectA == DBNull.Value && objectB == DBNull.Value )
{
return true;
}
if ( objectA == DBNull.Value || objectB == DBNull.Value )
{
return false;
}
return ( objectA.Equals( objectB ) );
}
private bool RowEqual(DataRow rowA, DataRow rowB, DataColumnCollection columns)
{
bool result = true;
for ( int i = 0; i < columns.Count; i++ )
{
result &= ColumnEqual( rowA[ columns[ i ].ColumnName ], rowB[ columns[ i ].ColumnName ] );
}
return result;
}
private void ParseFieldList(string fieldList, bool allowRelation)
{
if ( m_FieldList == fieldList )
{
return;
}
m_FieldInfo = new ArrayList();
m_FieldList = fieldList;
FieldInfo Field;
string[] FieldParts;
string[] Fields = fieldList.Split( ',' );
for ( int i = 0; i <= Fields.Length - 1; i++ )
{
Field = new FieldInfo();
FieldParts = Fields[ i ].Trim().Split( ' ' );
switch ( FieldParts.Length )
{
case 1:
//to be set at the end of the loop
break;
case 2:
Field.FieldAlias = FieldParts[ 1 ];
break;
default:
return;
}
FieldParts = FieldParts[ 0 ].Split( '.' );
switch ( FieldParts.Length )
{
case 1:
Field.FieldName = FieldParts[ 0 ];
break;
case 2:
if ( allowRelation == false )
{
return;
}
Field.RelationName = FieldParts[ 0 ].Trim();
Field.FieldName = FieldParts[ 1 ].Trim();
break;
default:
return;
}
if ( Field.FieldAlias == null )
{
Field.FieldAlias = Field.FieldName;
}
m_FieldInfo.Add( Field );
}
}
private DataTable CreateTable(string tableName, DataTable sourceTable, string fieldList)
{
DataTable dt;
if ( fieldList.Trim() == "" )
{
dt = sourceTable.Clone();
dt.TableName = tableName;
}
else
{
dt = new DataTable( tableName );
ParseFieldList( fieldList, false );
DataColumn dc;
foreach ( FieldInfo Field in m_FieldInfo )
{
dc = sourceTable.Columns[ Field.FieldName ];
DataColumn column = new DataColumn();
column.ColumnName = Field.FieldAlias;
column.DataType = dc.DataType;
column.MaxLength = dc.MaxLength;
column.Expression = dc.Expression;
dt.Columns.Add( column );
}
}
if ( ds != null )
{
ds.Tables.Add( dt );
}
return dt;
}
private void InsertInto(DataTable destTable, DataTable sourceTable,
string fieldList, string rowFilter, string sort)
{
ParseFieldList( fieldList, false );
DataRow[] rows = sourceTable.Select( rowFilter, sort );
DataRow destRow;
foreach ( DataRow sourceRow in rows )
{
destRow = destTable.NewRow();
if ( fieldList == "" )
{
foreach ( DataColumn dc in destRow.Table.Columns )
{
if ( dc.Expression == "" )
{
destRow[ dc ] = sourceRow[ dc.ColumnName ];
}
}
}
else
{
foreach ( FieldInfo field in m_FieldInfo )
{
destRow[ field.FieldAlias ] = sourceRow[ field.FieldName ];
}
}
destTable.Rows.Add( destRow );
}
}
private void ParseGroupByFieldList(string FieldList)
{
if ( GroupByFieldList == FieldList )
{
return;
}
GroupByFieldInfo = new ArrayList();
FieldInfo Field;
string[] FieldParts;
string[] Fields = FieldList.Split( ',' );
for ( int i = 0; i <= Fields.Length - 1; i++ )
{
Field = new FieldInfo();
FieldParts = Fields[ i ].Trim().Split( ' ' );
switch ( FieldParts.Length )
{
case 1:
//to be set at the end of the loop
break;
case 2:
Field.FieldAlias = FieldParts[ 1 ];
break;
default:
return;
}
FieldParts = FieldParts[ 0 ].Split( '(' );
switch ( FieldParts.Length )
{
case 1:
Field.FieldName = FieldParts[ 0 ];
break;
case 2:
Field.Aggregate = FieldParts[ 0 ].Trim().ToLower();
Field.FieldName = FieldParts[ 1 ].Trim( ' ', ')' );
break;
default:
return;
}
if ( Field.FieldAlias == null )
{
if ( Field.Aggregate == null )
{
Field.FieldAlias = Field.FieldName;
}
else
{
Field.FieldAlias = Field.Aggregate + "of" + Field.FieldName;
}
}
GroupByFieldInfo.Add( Field );
}
GroupByFieldList = FieldList;
}
private DataTable CreateGroupByTable(string tableName, DataTable sourceTable, string fieldList)
{
if ( fieldList == null || fieldList.Length == 0 )
{
return sourceTable.Clone();
}
else
{
DataTable dt = new DataTable( tableName );
ParseGroupByFieldList( fieldList );
foreach ( FieldInfo Field in GroupByFieldInfo )
{
DataColumn dc = sourceTable.Columns[ Field.FieldName ];
if ( Field.Aggregate == null )
{
dt.Columns.Add( Field.FieldAlias, dc.DataType, dc.Expression );
}
else
{
dt.Columns.Add( Field.FieldAlias, dc.DataType );
}
}
if ( ds != null )
{
ds.Tables.Add( dt );
}
return dt;
}
}
private void InsertGroupByInto(DataTable destTable, DataTable sourceTable, string fieldList,
string rowFilter, string groupBy)
{
if ( fieldList == null || fieldList.Length == 0 )
{
return;
}
ParseGroupByFieldList( fieldList );
ParseFieldList( groupBy, false );
DataRow[] rows = sourceTable.Select( rowFilter, groupBy );
DataRow lastSourceRow = null, destRow = null;
bool sameRow;
int rowCount = 0;
foreach ( DataRow sourceRow in rows )
{
sameRow = false;
if ( lastSourceRow != null )
{
sameRow = true;
foreach ( FieldInfo Field in m_FieldInfo )
{
if ( !ColumnEqual( lastSourceRow[ Field.FieldName ], sourceRow[ Field.FieldName ] ) )
{
sameRow = false;
break;
}
}
if ( !sameRow )
{
destTable.Rows.Add( destRow );
}
}
if ( !sameRow )
{
destRow = destTable.NewRow();
rowCount = 0;
}
rowCount += 1;
foreach ( FieldInfo field in GroupByFieldInfo )
{
switch ( field.Aggregate.ToLower() )
{
case null:
case "":
case "last":
destRow[ field.FieldAlias ] = sourceRow[ field.FieldName ];
break;
case "first":
if ( rowCount == 1 )
{
destRow[ field.FieldAlias ] = sourceRow[ field.FieldName ];
}
break;
case "count":
destRow[ field.FieldAlias ] = rowCount;
break;
case "sum":
destRow[ field.FieldAlias ] = Add( destRow[ field.FieldAlias ], sourceRow[ field.FieldName ] );
break;
case "max":
destRow[ field.FieldAlias ] = Max( destRow[ field.FieldAlias ], sourceRow[ field.FieldName ] );
break;
case "min":
if ( rowCount == 1 )
{
destRow[ field.FieldAlias ] = sourceRow[ field.FieldName ];
}
else
{
destRow[ field.FieldAlias ] = Min( destRow[ field.FieldAlias ], sourceRow[ field.FieldName ] );
}
break;
}
}
lastSourceRow = sourceRow;
}
if ( destRow != null )
{
destTable.Rows.Add( destRow );
}
}
private object Min(object a, object b)
{
if ( ( a is DBNull ) || ( b is DBNull ) )
{
return DBNull.Value;
}
if ( ( (IComparable) a ).CompareTo( b ) == -1 )
{
return a;
}
else
{
return b;
}
}
private object Max(object a, object b)
{
if ( a is DBNull )
{
return b;
}
if ( b is DBNull )
{
return a;
}
if ( ( (IComparable) a ).CompareTo( b ) == 1 )
{
return a;
}
else
{
return b;
}
}
private object Add(object a, object b)
{
if ( a is DBNull )
{
return b;
}
if ( b is DBNull )
{
return a;
}
return ( (decimal) a + (decimal) b );
}
private DataTable CreateJoinTable(string tableName, DataTable sourceTable, string fieldList)
{
if ( fieldList == null )
{
return sourceTable.Clone();
}
else
{
DataTable dt = new DataTable( tableName );
ParseFieldList( fieldList, true );
foreach ( FieldInfo field in m_FieldInfo )
{
if ( field.RelationName == null )
{
DataColumn dc = sourceTable.Columns[ field.FieldName ];
dt.Columns.Add( dc.ColumnName, dc.DataType, dc.Expression );
}
else
{
DataColumn dc = sourceTable.ParentRelations[ field.RelationName ].ParentTable.Columns[ field.FieldName ];
dt.Columns.Add( dc.ColumnName, dc.DataType, dc.Expression );
}
}
if ( ds != null )
{
ds.Tables.Add( dt );
}
return dt;
}
}
private void InsertJoinInto(DataTable destTable, DataTable sourceTable,
string fieldList, string rowFilter, string sort)
{
if ( fieldList == null )
{
return;
}
else
{
ParseFieldList( fieldList, true );
DataRow[] Rows = sourceTable.Select( rowFilter, sort );
foreach ( DataRow SourceRow in Rows )
{
DataRow DestRow = destTable.NewRow();
foreach ( FieldInfo Field in m_FieldInfo )
{
if ( Field.RelationName == null )
{
DestRow[ Field.FieldName ] = SourceRow[ Field.FieldName ];
}
else
{
DataRow ParentRow = SourceRow.GetParentRow( Field.RelationName );
DestRow[ Field.FieldName ] = ParentRow[ Field.FieldName ];
}
}
destTable.Rows.Add( DestRow );
}
}
}
#endregion
#region SelectDistinct / Distinct
/// <summary>
/// 按照fieldName从sourceTable中选择出不重复的行，
/// 相当于select distinct fieldName from sourceTable
/// </summary>
/// <param name="tableName">表名</param>
/// <param name="sourceTable">源DataTable</param>
/// <param name="fieldName">列名</param>
/// <returns>一个新的不含重复行的DataTable，列只包括fieldName指明的列</returns>
public DataTable SelectDistinct(string tableName, DataTable sourceTable, string fieldName)
{
DataTable dt = new DataTable( tableName );
dt.Columns.Add( fieldName, sourceTable.Columns[ fieldName ].DataType );
object lastValue = null;
foreach ( DataRow dr in sourceTable.Select( "", fieldName ) )
{
if ( lastValue == null || !( ColumnEqual( lastValue, dr[ fieldName ] ) ) )
{
lastValue = dr[ fieldName ];
dt.Rows.Add( new object[]{lastValue} );
}
}
if ( ds != null && !ds.Tables.Contains( tableName ) )
{
ds.Tables.Add( dt );
}
return dt;
}
/// <summary>
/// 按照fieldName从sourceTable中选择出不重复的行，
/// 相当于select distinct fieldName1,fieldName2,,fieldNamen from sourceTable
/// </summary>
/// <param name="tableName">表名</param>
/// <param name="sourceTable">源DataTable</param>
/// <param name="fieldNames">列名数组</param>
/// <returns>一个新的不含重复行的DataTable，列只包括fieldNames中指明的列</returns>
public DataTable SelectDistinct(string tableName, DataTable sourceTable, string[] fieldNames)
{
DataTable dt = new DataTable( tableName );
object[] values = new object[fieldNames.Length];
string fields = "";
for ( int i = 0; i < fieldNames.Length; i++ )
{
dt.Columns.Add( fieldNames[ i ], sourceTable.Columns[ fieldNames[ i ] ].DataType );
fields += fieldNames[ i ] + ",";
}
fields = fields.Remove( fields.Length - 1, 1 );
DataRow lastRow = null;
foreach ( DataRow dr in sourceTable.Select( "", fields ) )
{
if ( lastRow == null || !( RowEqual( lastRow, dr, dt.Columns ) ) )
{
lastRow = dr;
for ( int i = 0; i < fieldNames.Length; i++ )
{
values[ i ] = dr[ fieldNames[ i ] ];
}
dt.Rows.Add( values );
}
}
if ( ds != null && !ds.Tables.Contains( tableName ) )
{
ds.Tables.Add( dt );
}
return dt;
}
/// <summary>
/// 按照fieldName从sourceTable中选择出不重复的行，
/// 并且包含sourceTable中所有的列。
/// </summary>
/// <param name="tableName">表名</param>
/// <param name="sourceTable">源表</param>
/// <param name="fieldName">字段</param>
/// <returns>一个新的不含重复行的DataTable</returns>
public DataTable Distinct(string tableName, DataTable sourceTable, string fieldName)
{
DataTable dt = sourceTable.Clone();
dt.TableName = tableName;
object lastValue = null;
foreach ( DataRow dr in sourceTable.Select( "", fieldName ) )
{
if ( lastValue == null || !( ColumnEqual( lastValue, dr[ fieldName ] ) ) )
{
lastValue = dr[ fieldName ];
dt.Rows.Add( dr.ItemArray );
}
}
if ( ds != null && !ds.Tables.Contains( tableName ) )
{
ds.Tables.Add( dt );
}
return dt;
}
/// <summary>
/// 按照fieldNames从sourceTable中选择出不重复的行，
/// 并且包含sourceTable中所有的列。
/// </summary>
/// <param name="tableName">表名</param>
/// <param name="sourceTable">源表</param>
/// <param name="fieldNames">字段</param>
/// <returns>一个新的不含重复行的DataTable</returns>
public DataTable Distinct(string tableName, DataTable sourceTable, string[] fieldNames)
{
DataTable dt = sourceTable.Clone();
dt.TableName = tableName;
string fields = "";
for ( int i = 0; i < fieldNames.Length; i++ )
{
fields += fieldNames[ i ] + ",";
}
fields = fields.Remove( fields.Length - 1, 1 );
DataRow lastRow = null;
foreach ( DataRow dr in sourceTable.Select( "", fields ) )
{
if ( lastRow == null || !( RowEqual( lastRow, dr, dt.Columns ) ) )
{
lastRow = dr;
dt.Rows.Add( dr.ItemArray );
}
}
if ( ds != null && !ds.Tables.Contains( tableName ) )
{
ds.Tables.Add( dt );
}
return dt;
}
#endregion
#region Select Table Into
/// <summary>
/// 按sort排序，按rowFilter过滤sourceTable，
/// 复制fieldList中指明的字段的数据到新DataTable，并返回之
/// </summary>
/// <param name="tableName">表名</param>
/// <param name="sourceTable">源表</param>
/// <param name="fieldList">字段列表</param>
/// <param name="rowFilter">过滤条件</param>
/// <param name="sort">排序</param>
/// <returns>新DataTable</returns>
public DataTable SelectInto(string tableName, DataTable sourceTable,
string fieldList, string rowFilter, string sort)
{
DataTable dt = CreateTable( tableName, sourceTable, fieldList );
InsertInto( dt, sourceTable, fieldList, rowFilter, sort );
return dt;
}
#endregion
#region Group By Table
public DataTable SelectGroupByInto(string tableName, DataTable sourceTable, string fieldList,
string rowFilter, string groupBy)
{
DataTable dt = CreateGroupByTable( tableName, sourceTable, fieldList );
InsertGroupByInto( dt, sourceTable, fieldList, rowFilter, groupBy );
return dt;
}
#endregion
#region Join Tables
public DataTable SelectJoinInto(string tableName, DataTable sourceTable, string fieldList, string rowFilter, string sort)
{
DataTable dt = CreateJoinTable( tableName, sourceTable, fieldList );
InsertJoinInto( dt, sourceTable, fieldList, rowFilter, sort );
return dt;
}
#endregion
#region Create Table
public DataTable CreateTable(string tableName, string fieldList)
{
DataTable dt = new DataTable( tableName );
DataColumn dc;
string[] Fields = fieldList.Split( ',' );
string[] FieldsParts;
string Expression;
foreach ( string Field in Fields )
{
FieldsParts = Field.Trim().Split( " ".ToCharArray(), 3 ); // allow for spaces in the expression
// add fieldname and datatype
if ( FieldsParts.Length == 2 )
{
dc = dt.Columns.Add( FieldsParts[ 0 ].Trim(), Type.GetType( "System." + FieldsParts[ 1 ].Trim(), true, true ) );
dc.AllowDBNull = true;
}
else if ( FieldsParts.Length == 3 ) // add fieldname, datatype, and expression
{
Expression = FieldsParts[ 2 ].Trim();
if ( Expression.ToUpper() == "REQUIRED" )
{
dc = dt.Columns.Add( FieldsParts[ 0 ].Trim(), Type.GetType( "System." + FieldsParts[ 1 ].Trim(), true, true ) );
dc.AllowDBNull = false;
}
else
{
dc = dt.Columns.Add( FieldsParts[ 0 ].Trim(), Type.GetType( "System." + FieldsParts[ 1 ].Trim(), true, true ), Expression );
}
}
else
{
return null;
}
}
if ( ds != null )
{
ds.Tables.Add( dt );
}
return dt;
}
public DataTable CreateTable(string tableName, string fieldList, string keyFieldList)
{
DataTable dt = CreateTable( tableName, fieldList );
string[] KeyFields = keyFieldList.Split( ',' );
if ( KeyFields.Length > 0 )
{
DataColumn[] KeyFieldColumns = new DataColumn[KeyFields.Length];
int i;
for ( i = 1; i == KeyFields.Length - 1; ++i )
{
KeyFieldColumns[ i ] = dt.Columns[ KeyFields[ i ].Trim() ];
}
dt.PrimaryKey = KeyFieldColumns;
}
return dt;
}
#endregion
}
}