Question

I am using the following Shared Function to select a value from DB.My concern is that since shared functions are shared among all objects, can this happen that if two persons executes the function almost at a same time, the data will be over written??

I mean the value returned from the DB will be the result of the last (most recent) execution?

EG:

User 1 executes the function and should get “abcd”
User 2 executes the function and should get “1234”

User 2 executes the function before User 1 could complete executing the function.

But both the users get “1234”

Public Shared Function SelectScalar(ByVal _sql As String, ByVal _parameterNames() As String, ByVal _parameterVals() As String) As String
            Dim _returnVal As String
            Dim _connection As SqlConnection = Global.Connection.GetDbConnection()
            Dim _command As New SqlCommand(_sql, _connection)
            Dim _value As String

            Try
                If _parameterNames IsNot Nothing Then
                    For i = 0 To _parameterNames.Length - 1
                        _command.Parameters.AddWithValue(_parameterNames(i), _parameterVals(i))
                    Next
                End If

                _value = CStr(_command.ExecuteScalar)
                _returnVal = _value
            Catch ex As Exception
                _returnVal = Nothing
            Finally
                If _connection.State = ConnectionState.Open Then
                    _connection.Close()
                    _connection.Dispose()
                    _command.Dispose()
                End If
            End Try

            Return _returnVal
        End Function

Answer 1

Shared Functions does not share their “internal” state, like _returnVal. A separate instance of all local variables are created each time the method is called and each call keeps track of their own set of variables, no cross talking can occur when the variables are declared inside the Shared Function.