关于.NET DataTable合并的问题

///<summary>
/// 将两个列不同的DataTable合并成一个新的DataTable
///</summary>
///<param name="dt1">源表</param>
///<param name="dt2">需要合并的表</param>
///<param name="primaryKeys">需要排重的主要键列表（为空不排重）</param>
///<param name="maxRows">合并后Table的最大行数</param>
///<returns>合并后的datatable</returns>
public static DataTable MergeDataTable(DataTable dt1, DataTable dt2, string[] primaryKeys, int maxRows)
{
//判断是否需要合并
if (dt1 == null && dt2 == null)
{
return null;
}
if (dt1 == null && dt2 != null)
{
return dt2.Copy();
}
else if (dt1 != null && dt2 == null)
{
return dt1.Copy();
}
//复制dt1的数据
DataTable dt = dt1.Copy();
//补充dt2的结构（dt1中没有的列）到dt中
for (int i = 0; i < dt2.Columns.Count; i++)
{
string cName = dt2.Columns[i].ColumnName;
if (!dt.Columns.Contains(cName))
{
dt.Columns.Add(new DataColumn(cName));
}
}
//复制dt2的数据
if (dt2.Rows.Count > 0)
{

bool isNeedFilter = primaryKeys == null || primaryKeys.Length == 0 ? false : true;

int mergeTableNum = dt.Rows.Count;
for (int i = 0; i < dt2.Rows.Count && mergeTableNum < maxRows; i++)
{
bool isNeedAdd = true;
//如果需要排重时，判断是否需要添加当前行
if (isNeedFilter)
{
string filter = "";
string primaryValue = "";
bool isNeedQuotes = false;
for (int j = 0; j < primaryKeys.Length; j++)
{
Type t = dt2.Rows[0][primaryKeys[j]].GetType();
isNeedQuotes = t.Name == "String" ? true : false;
primaryValue = dt2.Rows[i][primaryKeys[j]].ToString();

if(isNeedQuotes)
{
filter += primaryKeys[j] + "='" + primaryValue + "'";
}
else
{
filter += (primaryKeys[j] + "=" + primaryValue);
}

if (j != primaryKeys.Length - 1)
{
filter += " and ";
}
}

DataRow[] drs = dt.Select(filter);
if (drs != null && drs.Length > 0)
{
isNeedAdd = false;
}
}
//添加数据
if (isNeedAdd)
{
DataRow dr = dt.NewRow();
for (int j = 0; j < dt.Columns.Count; j++)
{
string cName = dt.Columns[j].ColumnName;
if (dt2.Columns.Contains(cName))
{
//防止因同一字段不同类型赋值出错
if (dt2.Rows[i][cName] != null && dt2.Rows[i][cName] != DBNull.Value && dt2.Rows[i][cName].ToString() != "")
{
dr[cName] = dt2.Rows[i][cName];
}
}
}
dt.Rows.Add(dr);
mergeTableNum++;
}
}
}
return dt;
}