我们有时候需要对DataTable中数据进行Distinct处理，过滤掉重复的数据，本文给出了解决方法：
事例代码来源于:
Erik Porter"s Blog Select DISTINCT on DataTable
http://weblogs.asp.net/eporter/archive/2005/02/10/370548.aspx 以及 HOWTOVisualC # .NET 中实现 DataSet SELECTDISTINCT Helper 类
http://support.microsoft.com/?id=326176
/**////
/// 返回执行Select distinct后的DataTable
///
///
源数据表
///
字段集
///
private DataTable SelectDistinct(DataTable SourceTable, params string[] FieldNames)
{
object[] lastValues;
DataTable newTable;
DataRow[] orderedRows;
if (FieldNames == null || FieldNames.Length == 0)
throw new ArgumentNullException("FieldNames");
lastValues = new object[FieldNames.Length];
newTable = new DataTable();
foreach (string fieldName in FieldNames)
newTable.Columns.Add(fieldName, SourceTable.Columns[fieldName].DataType);
orderedRows = SourceTable.Select("", string.Join(",", FieldNames));
foreach (DataRow row in orderedRows)
{
if (!fieldValuesAreEqual(lastValues, row, FieldNames))
{
newTable.Rows.Add(createRowClone(row, newTable.NewRow(), FieldNames));
setLastValues(lastValues, row, FieldNames);
}
}
return newTable;
}
private bool fieldValuesAreEqual(object[] lastValues, DataRow currentRow, string[] fieldNames)
{
bool areEqual = true;
for (int i = 0; i < fieldNames.Length; i++)
{
if (lastValues[i] == null || !lastValues[i].Equals(currentRow[fieldNames[i]]))
{
areEqual = false;
break;
}
}
return areEqual;
}
private DataRow createRowClone(DataRow sourceRow, DataRow newRow, string[] fieldNames)
{
foreach (string field in fieldNames)
newRow[field] = sourceRow[field];
return newRow;
}
private void setLastValues(object[] lastValues, DataRow sourceRow, string[] fieldNames)
{
for (int i = 0; i < fieldNames.Length; i++)
lastValues[i] = sourceRow[fieldNames[i]];
}
使用:
DataTable dt=(System.Data.DataTable)this.ViewState["Mydt"];
string[] fileds={"Filed1","Filed2"};//DISTINCT字段数组
DataTable newdt=this.SelectDistinct(dt,fileds);//返回过滤后的DataTable
