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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)

转载 作者：qq735679552 更新时间：2022-09-29 22:32:09 26 4
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本文实例总结了asp.net DataTable相关操作。分享给大家供大家参考，具体如下:

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#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
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#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
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#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
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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
   }
}

希望本文所述对大家asp.net程序设计有所帮助.

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