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DataTable相关操作,筛选,取前N条数据,去重复行,获取指定列数据

2019-03-29 12:33:25 来源:www.anyuan2002.com 【
    #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 
  } 
}


DataTable相关操作,筛选,取前N条数据,去重复行,获取指定列数据

 
 

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Tags: 操作 相关 DATATABLE
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