When you want to pass ad hoc or user supplied values to your SQL command at run time, it is important to use parameters to represent them in order to prevent the possibility of your application being exposed to SQL injection attacks.
SQL injection occurs usually as a result of taking user input and concatenating it with hard coded SQL statements that form part of an application's code base. The user input has been crafted specifically to alter the SQL that the program's designer intended to execute. The canonical example used to illustrate the issue involves a login form.
Typically, a login form is designed to accept a user name and a password that uniquely identifies an individual. If a valid combination is presented, the user is authorised to access protected parts of the application. A vulnerable SQL statement designed to check that submitted credentials against those stored in the database might look like this:. The username and password variables represent the values submitted by the user.
They are concatenated with the SQL to generate the command that is executed. If those values are "mike" and "pass1" respectively, the generated SQL will be:.
The command, when executed should only return rows if a match for those values is found. The resulting SQL will become:. Additional SQL syntax has been injected into the statement to change its behaviour. The single quotes are string delimiters as far as T-SQL is concerned, and if you allow users to enter these without managing them, you are asking for potential trouble. Often, you will see well-meaning advice from people that you should escape single quotes, which converts them to literal values instead of SQL syntax:.
Indeed, this has the desired effect. The generated SQL will no longer return all rows in the database. However, this does not mitigate against all forms of SQL injection.
Consider the very common scenario where you are querying the database for an article, product or similar by ID. Typically, the ID is stored as a number - most of them are autogenerated by the database:. The value for the productid variable could come from a posted form, or a query string value - perhaps from a hyperlink on a previous page. It's easy for a malicious user to amend a query string value. Imagine that the malicious user appends ;drop table AspNetUsers-- on the end of the query string before requesting the page.
Now the generated SQL becomes. Any database that can manage batch commands i. Some people advise that you should validate all user input against a blacklist of SQL keywords and syntax, but the problem with this approach is that there are perfectly valid reasons for users to submit values that might include entries in the blacklist.
In addition, you will have to go back and patch your blacklist every time your database provider adds new keywords to their product as they improve its feature set.
Parameters are represented in the SQL command by placeholders, and the values are passed to the command within the DbCommand object's Parameters collection. The format of the placeholder is dependant on what the provider supports. The SqlClient provider supports named parameters, with the parameter name prefixed with an character.
The OleDb provider supports positional parameters. Values are passed to the SQL command based on matching the order in which they have been added to the parameters collection to the order in which placeholders appear in the SQL.
Parameter placeholders can be named anything, as long as the placeholder names don't match database object names columns, tables etc. Dapper also provides a DynamicParameters class, which represents a "bag" of parameter values. You can pass an object to its constructor. The DynamicParameters type provides an Add method, enabling you to pass explicit parameters, specifying the datatype, direction and size:.In this post I will show you an interesting problem that we experienced when querying a SQL Server database with Dapper.
I will use a simplified data model and a sample application so you could reproduce the issue on your own. Our sample table will look as follows:. Our sample application will return the number of executions for a query plan with a hash provided by the user:. After running the application with SQL Profiler listening, we should find in its log a query similar to the one below:. In SQL Server you may even end up with an index scan.
When looking closer at the query generated by Dapper we can see that the text parameters are by default sent as nvarcharswhen in our Stats table the item column is of type varchar. This forces SQL Server to convert a parameter from multi- to single-byte string. Fortunately, we can easily fix this by just informing Dapper that our parameter should be a single-byte string there is a special DbString type in Dapper for this purpose :.
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The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Problem is that LastModificationDate doesn't contain milliseconds. How it can be fixed? Learn more. Dapper strange behaviour with datetime2 Ask Question. Asked 6 months ago. Active 6 months ago. Viewed 72 times. Snorlax Snorlax 4 4 silver badges 15 15 bronze badges.
Also, just to stave off the obvious -- how have you verified "it doesn't contain milliseconds"? The default formatting of DateTime when displayed as a string doesn't normally show any milliseconds; you need an explicit formatting string with fff for that. Ok I just had to add: SqlMapper. Active Oldest Votes. The answer is: SqlMapper. DateTimeOffset. Larnu You didn't answer any of the comments above for clarification.
I'm going to say this might appear to work, but isn't the solution you need. This way you store not only the milliseconds but timezone information too. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.
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Changing the Dapper mapping for .net DateTime to use DbType DateTime2 and reinstating it back again
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The database I am working on uses underscores in all the column names. For my case I can write one mapper that will work for any select statement -- it just simply maps column names to property names with the underscores removed.
Dapper – JSON type custom mapper
One of the things I like about Dapper is that there are no setup calls required at all when you use the default mapper. I am desperately trying to hold on to that experience as much as possible, while using the custom ITypeMap. There is even more code when you start keeping track of which types have already been registered with SetTypeMap.
The best solution I have come up with so far is to wrap all the overrides of SqlMapper. Is there a better way of doing this? It seems like DapperExtensions has something like this in the AutoMapper, but it is not clear to me if that works with SqlMapper. It's been a while, but I've been busy with developing a small Dapper extension, allowing you to configure mappings between property names and database column names. Learn more. Asked 5 years, 11 months ago.
Active 4 years, 3 months ago.Samira zitouni animatrice
Viewed 2k times. I'm looking for a way to change the default implementation of ITypeMap used by Dapper. So instead of the elegant: connection. Mike Hixson Mike Hixson 3, 1 1 gold badge 10 10 silver badges 24 24 bronze badges. What's wrong with settings each type map at application startup? When you want something different than a default implementation, you usually always end up with configuring that somewhere.
I'm trying to avoid having any setup code, like the when using Dapper's default conventions. I literally have 's of differnt types that I need to setup if I did it this way. Basically, I want to be able define my own convention once. I don't really need to customize each POCOs mapping individually. Active Oldest Votes. Henk Mollema Henk Mollema I'm testing this extension now. It appears to be the best way yet to handle mappings without having to markup POCOs with attributes.
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SQL Server Dapper
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Dapper mapping String parameter as AnsiString
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CompareOrdinal x.Posted by: admin November 18, Leave a comment. Marc Gravell thanks, for reply. If you wanted you could get Phone and Email or even the whole inserted row:.
Also with this you can also return data of deleted or updated rows. Just be careful if you are using triggers because:. More on it in the docs: link.
February 21, c Leave a comment. Questions: Closed. This question needs to be more focused.Hbo 2 schedule
It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this p Questions: I really enjoy using the aggregate functions that C provides such as. Anybut I struggle to understand what my options are just looking from the method signature: Can someone help me be Your email address will not be published.
Save my name, email, and website in this browser for the next time I comment. Add menu. How do I perform an insert and return inserted identity with Dapper? Single. Open ; conn. Any function in C February 21, c Leave a comment Questions: I really enjoy using the aggregate functions that C provides such as.
Leave a Reply Cancel reply Your email address will not be published.Add database column name as ColumnAttribute's Name property and add the attribute to properties to be mapped to. For class libraries of. Or you can find the classes to which ColumnAttribute is applied through reflection and set type mappings.
You must implement this. Thanks for the mapper class! Project builds but fails on runtime: System. SqlException : Invalid column name 'xyz Please check the TestCustomTypeMap test samples for preferred way of doing custom typemapping with a DescriptionAttribute.
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GetValue attr. GetSetMethod true : prop. GetProperty prop.
NameBindingFlags. GetSetMethod true! FindConstructor namestypes ; if result! GetConstructorParameter constructorcolumnName ; if result! GetMember columnName ; if result!How many flipflops are required to divide a signal frequency by 4
This comment has been minimized. Sign in to view. Copy link Quote reply. GetAssembly typeof Initiator. GetCustomAttributes false. SetTypeMap mappedTypeActivator.
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