去除DataTable中的重复行

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#region 过滤DataTable中的指定字段重复的行

/// <summary>
/// 过滤DataTable中的指定字段重复的行
/// </summary>
/// <param name= "dt "> </param>
/// <param name= "FieldName "> </param>
/// <returns> </returns>
public DataTable SelectDistinctByField(DataTable dt, string FieldName)
{
DataTable returnDt = new DataTable();
returnDt = dt.Copy();//将原DataTable复制一个新的
DataRow[] drs = returnDt.Select( " ", FieldName);//将DataTable按指定的字段排序
object LastValue = null;
for(int i = 0; i < drs.Length; i++)
{
if((LastValue == null) || (!(ColumnEqual(LastValue, drs[i][FieldName]))))
{
LastValue = drs[i][FieldName];
continue;
}

drs[i].Delete();
}

return returnDt;
}

private bool ColumnEqual(object A, object B)
{
// Compares two values to see if they are equal. Also compares DBNULL.Value.
// Note: If your DataTable contains object fields, then you must extend this
// function to handle them in a meaningful way if you intend to group on them.

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
}

#endregion