SqlConnection con=new SqlConnection(@"server=wjs08;uid=sa;pwd=dw;database=Northwind;");
con.Open();
SqlDataAdapter DaCustomers=new SqlDataAdapter("select * from customers",con);
SqlDataAdapter DaOrders=new SqlDataAdapter("select * from orders",con);
DaCustomers.Fill(ds,"customers");
DaOrders.Fill(ds,"orders");
DataRelation datarelationco=new DataRelation("DataRelationco",ds.Tables["customers"].Columns["CustomersID"],ds.Tables["orders"].Columns["CustomersID"]);
ds.Relations.Add(datarelationco);
dataGrid1.DataSource=ds;
dataGrid1.DataMember=ds.Tables["orders"].TableName;
上面这段代码执行到红色部分提示错误
未处理的“System.ArgumentNullException”类型的异常出现在 system.data.dll 中。

其他信息: “column”参数不能为空。
是怎么回事呢？

SqlConnection con=new SqlConnection(@"server=wjs08;uid=sa;pwd=dw;database=Northwind;");
con.Open();
SqlDataAdapter DaCustomers=new SqlDataAdapter("select * from customers",con);
SqlDataAdapter DaOrders=new SqlDataAdapter("select * from orders",con);
DaCustomers.Fill(ds,"customers");
DaOrders.Fill(ds,"orders");
DataRelation datarelationco=new DataRelation("DataRelationco",ds.Tables["customers"].Columns["CustomerID"],ds.Tables["orders"].Columns["CustomerID"]);
ds.Relations.Add(datarelationco);
dataGrid1.DataSource=ds;
dataGrid1.DataMember=ds.Tables["orders"].TableName;

把列名搞清楚

DataRelation datarelationco=new DataRelation("DataRelationco",ds.Tables["customers"].Columns["CustomerID"],ds.Tables["orders"].Columns["CustomerID"],false);这样就行了