C＃多个表，联接和自定义列

Question

尝试在VS2015上的C＃中将两个表连接在一起。

我可以获得字段ID以匹配字段名称，但我想将4个字段计算为一个标题但我正在努力这样做。

这是我目前的陈述。

var select = "SELECT fieldCosts.fieldCostID, fieldDetails.fieldName, fieldCosts.cropType, fieldCosts.cultivationCosts, fieldCosts.SeedCosts, SprayCosts as fieldCosts.spray1Costs + fieldCosts.spray2Costs + fieldCosts.spray3Costs + fieldCosts.spray4Costs FROM fieldCosts join fieldDetails on fieldDetails.fieldID = fieldDetails.fieldID order by fieldCosts.fieldCostID"; 

这是填充Datagrid的完整文本块

var select = "SELECT fieldCosts.fieldCostID, fieldDetails.fieldName, fieldCosts.cropType, fieldCosts.cultivationCosts, fieldCosts.SeedCosts, SprayCosts as fieldCosts.spray1Costs + fieldCosts.spray2Costs + fieldCosts.spray3Costs + fieldCosts.spray4Costs FROM fieldCosts join fieldDetails on fieldDetails.fieldID = fieldDetails.fieldID order by fieldCosts.fieldCostID";

var c = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=H:\School\Magee\Project\Programme\Farm Costs\Farm Costs\farmCosts.mdf;Integrated Security=True"); // Your Connection String here

var dataAdapter = new SqlDataAdapter(select, c);

var commandBuilder = new SqlCommandBuilder(dataAdapter);
var ds = new DataSet();
dataAdapter.Fill(ds);
dgFieldDetails.ReadOnly = true;
dgFieldDetails.DataSource = ds.Tables[0];

当我在不尝试计算任何列的情况下执行代码时，它会向我显示所有三个字段，但我只在字段上有一个条目。成本表