Are static methods in ASP.NET code-behind classes non-thread-safe?

Question

Can I use static methods in my ASP.NET Pages and UserControls classes if they don't use any instance members? I.e.:

protected void gridView_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
 gridStatement.DataSource = CreateDataSource();
 gridStatement.PageIndex = e.NewPageIndex;
 gridStatement.DataBind();
}
private static DataTable CreateDataSource()
{
 using (var command = new SqlCommand("SELECT foobar"))
 {
 var table = new DataTable();
 new SqlDataAdapter(command).Fill(table);
 return table;
 }
}

Or this is not thread-safe?

• Kane: What type of variable is the "command" object?

Answer 1

Yes, you can use static methods - they are thread-safe. Each thread will execute in a separate context and therefore any objects created inside a static method will only belong to that thread.

You only need to worry if a static method is accessing a static field, such as a list. But in your example the code is definitely thread-safe.

• Matthew: I think your comment "you can use static members" is incorrect. A "member" is a field, property, or method. So by that definition a static member (variable) and a static field are the same thing. Maybe you meant to say it's ok to use static methods. The statement about any objects created in a static method will only belong to that thread is misleading. Any instance variable (non-static) is threadsafe regardless of if the method is static or not. A static method just means that the code is static; it says nothing about the variables.

Answer 2

nothing shared across threads, so it is thread safe. unless you access static members that other static methods have a chance of executing concurrently with it...

Answer 3

it is. The only thing to worry about in your context about thread-safeness is a concept that involves static members, as already said. When any method (static or not) accesses a static member, you should worry about multithreading issues. Consider the following:

public class RaceConditionSample
{
 private static int number = 0;
 public static int Addition()
 {
 int x = RaceConditionSample.number;
 x = x + 1;
 RaceConditionSample.number = x;
 return RaceConditionSample.number;
 }
 public int Set()
 {
 RaceConditionSample.number = 42;
 return RaceConditionSample.number;
 }
 public int Reset()
 {
 RaceConditionSample.number = 0;
 return RaceConditionSample.number;
 }
}
RaceConditionSample sample = new RaceConditionSample();
System.Diagostics.Debug.WriteLine(sample.Set());
// Consider the following two lines are called in different threads in any order, Waht will be the
// output in either order and/or with any "interweaving" of the individual instructions...?
System.Diagostics.Debug.WriteLine(RaceConditionSample.Addition());
System.Diagostics.Debug.WriteLine(sample.Reset());

The answer is: It may be "42, 43, 0", "42, 0, 1" you wont know before..