在DataTable中实现DataTable.Select("Distinct")功能
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
/// <summary>
/// 返回执行Select distinct后的DataTable
/// </summary>
/// <param name="SourceTable">源数据表</param>
/// <param name="FieldNames">字段集</param>
/// <returns></returns>
private DataTable SelectDistinct(DataTable SourceTable, params string[] FieldNames)
{
object[] lastValues;
DataTable newTable;
DataRow[] orderedRows;
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if (FieldNames == null || FieldNames.Length == 0)
throw new ArgumentNullException("FieldNames");
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lastValues = new object[FieldNames.Length];
newTable = new DataTable();
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foreach (string fieldName in FieldNames)
newTable.Columns.Add(fieldName, SourceTable.Columns[fieldName].DataType);
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orderedRows = SourceTable.Select("", string.Join(",", FieldNames));
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foreach (DataRow row in orderedRows)
{
if (!fieldValuesAreEqual(lastValues, row, FieldNames))
{
newTable.Rows.Add(createRowClone(row, newTable.NewRow(), FieldNames));
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setLastValues(lastValues, row, FieldNames);
}
}
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return newTable;
}
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private bool fieldValuesAreEqual(object[] lastValues, DataRow currentRow, string[] fieldNames)
{
bool areEqual = true;
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for (int i = 0; i < fieldNames.Length; i++)
{
if (lastValues[i] == null || !lastValues[i].Equals(currentRow[fieldNames[i]]))
{
areEqual = false;
break;
}
}
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return areEqual;
}
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private DataRow createRowClone(DataRow sourceRow, DataRow newRow, string[] fieldNames)
{
foreach (string field in fieldNames)
newRow[field] = sourceRow[field];
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return newRow;
}
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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
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
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