在下面的例子中實現(xiàn)了3個join方法，其目的是把兩個datatable連接起來，相當于sql的inner join方法，返回datatable的所有列。
如果兩個datatable中的datacolumn有重復(fù)的話，把第二個設(shè)置為columnname+"_second",下面是代碼，希望對大家有所幫助。
using system;
using system.data;
namespace windowsapplication1
{
public class sqlops
{
public sqlops()
{
}
public static datatable join (datatable first, datatable second, datacolumn[] fjc, datacolumn[] sjc)
{
//創(chuàng)建一個新的datatable
datatable table = new datatable("join");
// use a dataset to leverage datarelation
using(dataset ds = new dataset())
{
//把datatable copy到dataset中
ds.tables.addrange(new datatable[]{first.copy(),second.copy()});
datacolumn[] parentcolumns = new datacolumn[fjc.length];
for(int i = 0; i < parentcolumns.length; i++)
{
parentcolumns[i] = ds.tables[0].columns[fjc[i].columnname];
}
datacolumn[] childcolumns = new datacolumn[sjc.length];
for(int i = 0; i < childcolumns.length; i++)
{
childcolumns[i] = ds.tables[1].columns[sjc[i].columnname];
}
//創(chuàng)建關(guān)聯(lián)
datarelation r = new datarelation(string.empty,parentcolumns,childcolumns,false);
ds.relations.add(r);
//為關(guān)聯(lián)表創(chuàng)建列
for(int i = 0; i < first.columns.count; i++)
{
table.columns.add(first.columns[i].columnname, first.columns[i].datatype);
}
for(int i = 0; i < second.columns.count; i++)
{
//看看有沒有重復(fù)的列，如果有在第二個datatable的column的列明后加_second
if(!table.columns.contains(second.columns[i].columnname))
table.columns.add(second.columns[i].columnname, second.columns[i].datatype);
else
table.columns.add(second.columns[i].columnname + "_second", second.columns[i].datatype);
}
table.beginloaddata();
foreach(datarow firstrow in ds.tables[0].rows)
{
//得到行的數(shù)據(jù)
datarow[] childrows = firstrow.getchildrows(r);
if(childrows != null && childrows.length > 0)
{
object[] parentarray = firstrow.itemarray;
foreach(datarow secondrow in childrows)
{
object[] secondarray = secondrow.itemarray;
object[] joinarray = new object[parentarray.length+secondarray.length];
array.copy(parentarray,0,joinarray,0,parentarray.length);
array.copy(secondarray,0,joinarray,parentarray.length,secondarray.length);
table.loaddatarow(joinarray,true);
}
}
}
table.endloaddata();
}
return table;
}
public static datatable join (datatable first, datatable second, datacolumn fjc, datacolumn sjc)
{
return join(first, second, new datacolumn[]{fjc}, new datacolumn[]{sjc});
}
public static datatable join (datatable first, datatable second, string fjc, string sjc)
{
return join(first, second, new datacolumn[]{first.columns[fjc]}, new datacolumn[]{first.columns[sjc]});
}
}
}
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