我在sql中有一个检查用户名和密码是否正确的函数，返回1或0

CREATE Function [dbo].[checklogin](@user varchar(30),@pass varchar(30))
Returns  BIT  
AS 
BEGIN  
DECLARE @check as bit
if (SELECT count(*) from dbo.Users where dbo.USERS.user_name= @user and  dbo.USERS.user_password=@pass)=1
set @check = 1
else
set @check=0
Return @check
END

在没有sql的情况下调用此函数时，linq返回实际信息

Sub loginCheck(ByVal username As String, ByVal password As String, ByVal frm As Form)

        Using con As New SqlConnection(inform.connectionstring)//
            con.Open()
            Using cmd As New SqlCommand("select dbo.checklogin('Manager','123');", con)
                Dim a As Boolean = CBool(cmd.ExecuteScalar)
                If a Then
                    MsgBox("Success")
                Else
                    MsgBox("Failed")
                End If
            End Using

        End Using
    End Sub

但是当我需要使用linq时，总是返回false

Sub loginCheck(ByVal username As String, ByVal password As String, ByVal frm As Form)

        Using con As New SqlConnection(inform.connectionstring)
            con.Open()
            Dim dta As New DataAj
            Dim ab As Boolean = dta.checklogin(username, password).Value
            If ab Then
                MsgBox("Success")
            Else
                MsgBox("Failed")
            End If

        End Using
    End Sub