C#中类型转换为SQL数据

Question

I have a DataTable which is filled from a SQL database. Values are returned as object type (also the Calculate function returns object as well for some reason), so I need to convert them to proper type. It makes the code so complicated.

Like this:

 double value;

 foreach (DataRow row in sampleDataTable.Rows)
 {
     value +=  (double)Global.Calculate(Convert.ToDouble(Global.dbNullCheck(row["value1"], 0)) / Convert.ToDouble(row["value2"]), 2);
 }

I can write above code as:

 double sum;
 double value1;
 double value2;

 foreach (DataRow row in sampleDataTable.Rows)
 {
     value1 = Convert.ToDouble(Global.dbNullCheck(row["value1"], 0);
     value2 = Convert.ToDouble(row["value2"]);
     sum +=  (double)Global.Calculate(value1 / value2, 2);
 }

But of course, it is still not clear and I am doing something wrong. I need to check all values if they are DBNull and after that I need to convert them. Any ideas how can I improve this type of code? It's all around my code:)

Is there a good way to handle SQL data?

Answer 1

Don't think in terms of "convert". These objects are already the types you want; it's just the ADO.Net library can't know in advance what type to use. So instead of a conversion, which can be relatively slow, you need a cast .

Additionally, in general you don't want to think initially in terms of individual columns. Instead, define a class object to represent each row. Then create a function that accepts a DataRow as an argument and returns an instance of this new class as a result. This function will need to know what to do with individual columns, but the larger foreach loop (or similar) should just be calling this function.