C# 如何去掉DataTable中的重复行

.net 1.1中的解决方法
1建立一个DataSetHelper类(DataSetHelper.cs)
 

  public class DataSetHelper
  {
     public DataSet ds;
     public DataSetHelper(ref DataSet DataSet)
      {
         ds = DataSet;
     }
     public DataSetHelper()
      {
         ds = null;
     }
     private bool ColumnEqual(object A, object B)
      {
         if (A == DBNull.Value && B == DBNull.Value) //  both are DBNull.Value
             return true;
         if (A == DBNull.Value || B == DBNull.Value) //  only one is DBNull.Value
             return false;
         return (A.Equals(B));  // value type standard comparison
     }
     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.Add(dt);
         return dt;
     }
 }

 2 建立一个Web窗体，在page_load中写下面的代码
       

         DataSet ds;
         DataSetHelper dsHelper;
         ds = new DataSet();
         dsHelper = new DataSetHelper(ref ds);
 
         // Create source table
         DataTable dt = new DataTable("Orders");
         dt.Columns.Add("EmployeeID", Type.GetType("System.String"));
         dt.Columns.Add("OrderID", Type.GetType("System.Int32"));
         dt.Columns.Add("Amount", Type.GetType("System.Decimal"));
 
          dt.Rows.Add(new object[] { "Sam", 5, 25.00 });
          dt.Rows.Add(new object[] { "Tom", 7, 50.00 });
          dt.Rows.Add(new object[] { "Sue", 9, 11.00 });
          dt.Rows.Add(new Object[] { "Tom", 12, 7.00 });
          dt.Rows.Add(new Object[] { "Sam", 14, 512.00 });
          dt.Rows.Add(new Object[] { "Sue", 15, 17.00 });
          dt.Rows.Add(new Object[] { "Sue", 22, 2.50 });
          dt.Rows.Add(new object[] { "Tom", 24, 3.00 });
          dt.Rows.Add(new object[] { "Tom", 33, 78.75 });
 
         ds.Tables.Add(dt);
        DataTable td=dsHelper.SelectDistinct("DistinctEmployees", ds.Tables["Orders"], "EmployeeID");
        this.GridView1.DataSource = td;
        this.GridView1.DataBind();

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 .net 2.0中的解决方法

 

          public DataTable GetTopSearch()
          {
             DataSet dsKeyword = dal.GetKeyword();
             DataSet dsTopSearch = new DataSet();
             for (int i = 0; i < 4; i++)
              {
                 string keyword = dsKeyword.Tables[0].Rows[i]["Name"].ToString();
                 string condition = dsKeyword.Tables[0].Rows[i]["SearchCondition"].ToString();
                 dsTopSearch.Merge(dal.GetTopSearch(keyword,condition));
             }
             return dsTopSearch.Tables[0].DefaultView.ToTable(true, "ID","Name","Author","Publisher","PublishDate","TypeName","Price","SalePrice","SavePrice","Rebate","ImagePath","ContentIntro");
         }