Piece of code analysis

Guest User

Hi,

Id like to know what this piece of code is doing please. My comments are next to each expression as to what I think is happening.

// Resetting the generic type T and assigning to a local variable t

T t = default(T);

// Assigning the ExecuteReader method to a local variable named reader in order to get the result of the command.

var reader = command.ExecuteReader();

// Whilst the reader variable is reading the rows.

if (reader.Read())

// Pass the reader variable to the make method and assign it to t.

t = make(reader);

// return the value type t.

return t;

This is the Method signature declaration

public static T ReadList(Func make)

3 Replies

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Vulpes14y ago
Accepted answer
I think you've grasped what it's doing though I've made some slight changes to your comments.

// Sets the local variable t to the default value of the type parameter, T

T t = default(T);

// Assigns the return value of the ExecuteReader method to a local variable named reader

var reader = command.ExecuteReader();

// Whilst the reader variable is reading the rows.

if (reader.Read())

// Passes the reader variable to the make method and assign it's return value to t.

t = make(reader);

// Returns the value of t.

return t;

This makes sense because 'make' is a delegate for a method which takes an IDataReader and returns a value of type T and the ReadList method itself also returns a value of type T.
Vulpes14y ago
It's just a local variable declaration, like for instance:

int t = default(int);

which would set 't' to zero which is the default value for ints.

The only difference here is that the type is a type parameter, T:

T t = default(T);

If T happened to be int, then this line would be equivalent to the earlier one.

If T were string, then we would have:

string t = null; // because default(string) is null
Guest User14y ago
Hi Vulpes

With reference to your comment

// Sets the local variable t to the default value of the type parameter, T

T t = default(T);

I was under the impression that if a type is declared before a variable ie T t, its effectively "Getting" so that the t reference can be returned with a return statement ie return t;

With the opposite being the "Setting" like so...

t = default(T);

or even further down in the code

// Passing the reader reference to the make method and "Setting" to local variable t.

t = make(reader);

Thanks