Requires that my function is implemented access to the database - database

Question

Requires that my function is implemented access to the databaseand certain operations were carried out.
Such as:
1) Check or read the message.
2) Checking and issuing all communications between users by date.
3) Find the latest posts from all users.
But I though there is material in the tutorial I could not figure out how to do. All I could show you. Therefore, I want to ask you to see my code and see what's up there and help me out. You do not need to completely write code. Just if it's not hard for you to sink your sleeves and calmly give examples let me write these three functions on LINQ and EntityFramework
MY CODE:
public bool CheckIfUnreadMessagesArePresent(int userId)
{
IList<MessageInfo> messageInfo = new List<MessageInfo>();
MessageInfo messageIn = new MessageInfo();
var sql = #"SELECT * FROM MessageInfo
WHERE wasRead = 0 AND Id = #userId ORDER BY date DESC";
var meassage = dataBaseContext.Database.SqlQuery<MessageInfo>(sql, new { userId = messageIn.Id });
return messageInfo.Any(messageIn.WasRead == true);
}
public IList<UserInfo> FetchMessagesFromConversation(int userID1, int userID2)
{
IList<UserInfo> messageInfo = new List<UserInfo>();
MessageInfo messageIn = new MessageInfo();
var sql = #"SELECT * FROM MessageInfo
WHERE userID1 = 1 AND userID2 = 3 OR userID1 = 3 AND userID2 = 1 order by date DESC";
var meassage = dataBaseContext.Database.SqlQuery<MessageInfo>(sql, new { userID1 = messageIn.SenderId,userID2 = messageIn.ReceiverId});
messageInfo.Insert(message);
return messageInfo;
}
public IList<MessageInfo> FetchLastMessageFromEachConversation((int userID))
{
IList<UserInfo> messageInfo = new List<UserInfo>();
MessageInfo messageIn = new MessageInfo();
var sql = #"SELECT * FROM MessageInfo
WHERE date IN (#SELECT max(date)
FROM MessageInfo WHRERE date IN (
SELECT max(date)
FROM MessageInfo
GROUP BY messageIn.ID, messageIn.ReceiverId
ORDER BY date DESC, messageIn.ID, messageIn.ReceiverId)
GROUP BY if (messageIn.ID < messageIn.ReceiverId,
concat(messageIn.ID, " - ", messageIn.ReceiverId), concat(messageIn.ReceiverId, " - ", messageIn.ID)))";
var meassage = dataBaseContext.Database.SqlQuery<MessageInfo>(sql, new { userID1 = messageIn.SenderId, userID2 = messageIn.ReceiverId });
return messageInfo;
}
My DataBase
CREATE TABLE [dbo].[UserInfo](
[Id] [int] IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Login] [varchar](50) NOT NULL,
[Password] [varchar](50) NOT NULL,
[FirstName] [nchar](10) NOT NULL,
[LastName] [nchar](10) NOT NULL,
[Email] [varchar](50) NOT NULL,
[RegistrationDate] [datetime] NOT NULL,
)
GO
CREATE TABLE [dbo].[Messages](
[Id] [int] IDENTITY(1,1) PRIMARY KEY NOT NULL,
[SenderId] [int] NOT NULL,
[ReceiverId] [int] NOT NULL,
[Message] [varchar](500) NOT NULL,
[date] [datetime] NOT NULL,
[WasRead][bit] NOT NULL
CONSTRAINT FK_UserInfoSender FOREIGN KEY (SenderId)
REFERENCES [UserInfo](Id),
CONSTRAINT FK_UserInfoReceiver FOREIGN KEY (ReceiverId)
REFERENCES [UserInfo](Id)
)
GO