I need to do an update but the column name is dynamic.
Code Snippet:
using (var cn = Connection)
{
var sql = #"UPDATE Teste
SET #columnName = #parameter,
DT_PROCESSAMENTO = #vDtProcessamento
WHERE ID = #ID";
var resultado = cn.Execute(sql, new
{
columnName,
parameter,
ID
});
}
Is it possible to pass the column name as a parameter?
This code is what I did, but it does not work. No exceptions but the update does not work.
You should use String.Format:
var columnName = "Name";
var sql = String.Format(#"UPDATE Teste
SET {0} = #parameter
WHERE ID = #ID", columnName);
But here you can get SQL injection.
So it's better to check that column name is really column name in your table.
No you cannot do that that way because the column name cannot be a variable.
To do it you do need dynamic SQL like this:
using (var cn = Connection)
{
var sql = $#"UPDATE Teste
SET {columnName} = #parameter,
DT_PROCESSAMENTO = #vDtProcessamento
WHERE ID = #ID";
var resultado = cn.Execute(sql, new
{
parameter,
ID
});
}
In the above snippet code you can combine # to use linebreaks inside the string and $ to insert variables in the string - it's a bit clearer and shorter than using String.Format.
I already use something like this with dapper for a few specific scenarios.
As noted, to do this you need to dynamically construct your SQL, either in SQL then use EXEC(), or in your C# with string.Format() or StringBuilder. Just be aware that by doing this, you will identify yourself as a savage in the eyes of some people! You have no guarantee that users of your method will provide a valid column name. You have to run your program to see what SQL it generates, and if it runs. You have no type safety around the input parameter. There must be a better way. disclaimer: I wrote QueryFirst
Using Database.Query has has made a huge improvement on readability in my code:
String Select = 'sp_getAllUsers';
WebMatrix.Data.Database DB = WebMatrix.Data.Database.Open(MyConString);
var data = DB.Query(Select);
I'd like to switch to a non-stored procedure query. The MSDN says there's an optional parameter to the Query Method, Object[], that can be passed as SQL parameters, however they don't have any further information about it.
So I have two questions:
How can I create a Object[]?
Will adding parameters in this way prevent hacking threats, such as SQL Injection?
Here's an abridged version of what I have tried:
Select = "Select * From Users Where first_name = "Foo" AND last_name = "Bar"
// Like Javascript
Object[] params = {"first_name" : "Foo"}, {"last_name" : "Bar"};
// More Like What I think it will be
Object[] Params = (String Name = "first_name", String First_Name = "Foo");
var data = DB.Query(Select, params);
All the sources I've looked at only seem to reference the old way. This is close, but he doesn't use the parameter parameter of the Query method.
Try using this syntax:
string selectCommand = "sp_getAllUsers(#0, #1)";
// selectCommand = "Select * From Users Where first_name = #0 AND last_name = #1";
...
var data = DB.Query(selectCommand, "Foo", "Bar");
More info, see:
http://www.aspnet101.com/2010/07/webmatrix-tutorial-working-with-data/
Also, using a Parameter will always prevent SQL Injection as it always double quote a single quote.
I've heard of parametized sql queries a long time ago but I never really gave any attention to it as I'm used to writing full sql statements. I know it improves security against sql injection so now might be a very good time to adapt change even if it's too late. I got this one from this site http://www.codinghorror.com/blog/2005/04/give-me-parameterized-sql-or-give-me-death.html. So all credits go to the author. I've noticed all examples of parametized sql queries have paremeter count limitations. An example is the one shown below.
SqlConnection conn = new SqlConnection(_connectionString);
conn.Open();
string s = "SELECT email, passwd, login_id, full_name FROM members WHERE email = #email";
SqlCommand cmd = new SqlCommand(s);
cmd.Parameters.Add("#email", email);
SqlDataReader reader = cmd.ExecuteReader();
This is just equivalent to
SELECT email, passwd, login_id, full_name FROM members WHERE email = 'x';
I've learned programming all on my own through reading online tutorials and I really got nobody to help me on this. The reason I got stuck with full sql statement queries is the fact that I can't figure out how to do parametized sql queries with unlimited parameters. Is there any way to do this? The example only accepts 1 parameter which is the 'email' field. And it selects 4 fields from the given sql statement. My question is... is there any way we can do parametized sql queries with 5, 6, 7, or 100 selected fields, as well as the conditions under the WHERE clause? If this is possible, it will be particularly helpful when using INSERT statement. Thank you very much.
This example is in C#, but any VB.NET or same C# implementations are greatly appreciated. Thanks.
One possible solution would be to pass the parameters name and value using a Dictionary object. A Dictionary object holds a collection of keys and values, and this is exactly what a single SqlParameter is - a single Key/Value container in the form:
Key = #Value
A collection can hold an arbitrary count of items, for example:
new Dictionary<String, Object>
{
{ "#Name", "Anonymous" },
{ "#Age", 25 },
{ "#Street", "Highway" },
{ "#Number", "1001" },
{ "#City", "NoName" }
}
In the example above, the key is of type String and the value of type Object. Object allows parameter values of arbitrary types (the explanation comes later in the code examples).
One possibility to create dynamic SQL statements would be:
extract the repetitive tasks, for example the creation of the SqlCommand and the passing of the parameters to the SqlCommand variable
create parametrised dynamic SQL query string for the wanted SQL command
The code can look like this:
// extract all repetitive tasks
// Create an array of SqlParameters from the given Dictionary object.
// The parameter value is of type Object in order to allow parameter values of arbitrary types!
// The .NET Framework converts the value automatically to the correct DB type.
// MSDN info: http://msdn.microsoft.com/en-us/library/0881fz2y%28v=vs.110%29.aspx
private SqlParameter[] dictionaryToSqlParameterArray(Dictionary<string, object> parameters)
{
var sqlParameterCollection = new List<SqlParameter>();
foreach (var parameter in parameters)
{
sqlParameterCollection.Add(new SqlParameter(parameter.Key, parameter.Value));
}
return sqlParameterCollection.ToArray();
}
// sqlQuery is the complete parametrised query
// for example like: INSERT INTO People(Name, Age, Street) VALUES(#Name, #Age, #Street)
private SqlCommand createSqlCommand(String sqlQuery, Dictionary<String, object> parameters)
{
SqlCommand command = new SqlCommand(sqlQuery);
command.Parameters.AddRange(dictionaryToSqlParameterArray(parameters));
return command;
}
Now a call with dynamic count of parameters will look like this:
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
string sqlQuery = "SELECT email, passwd, login_id, full_name FROM members WHERE email = #email AND name = #name";
// using the newly created method instead of adding/writing every single parameter manually
SqlCommand command = createSqlCommand(sqlQuery, new Dictionary<String, Object>
{
{ "#email", "test#test.com" },
{ "#name", "test" }
});
SqlDataReader reader = command.ExecuteReader();
It is a good start, but this is still not very dynamic, since we need to write the complete query every time (we save only the typing of command.Parameters.Add). Let's change this in order to type even less:
// create a parametrised SQL insert command with arbitrary count of parameters for the given table
private SqlCommand createSqlInsert(String tableName, Dictionary<String, object> parameters)
{
// the sql insert command pattern
var insertQuery = #"INSERT INTO {0}({1}) VALUES({2})";
// comma separated column names like: Column1, Column2, Column3, etc.
var columnNames = parameters.Select (p => p.Key.Substring(1)).Aggregate ((h, t) => String.Format("{0}, {1}", h, t));
// comma separated parameter names like: #Parameter1, #Parameter2, etc.
var parameterNames = parameters.Select (p => p.Key).Aggregate ((h, t) => String.Format("{0}, {1}", h, t));
// build the complete query
var sqlQuery = String.Format(insertQuery, tableName, columnNames, parameterNames);
// debug
Console.WriteLine(sqlQuery);
// return the new dynamic query
return createSqlCommand(sqlQuery, parameters);
}
// create a parametrised SQL select/where command with arbitrary count of parameters for the given table
private SqlCommand createSqlWhere(String tableName, Dictionary<String, object> parameters)
{
// the sql select command pattern
var whereQuery = #"SELECT * FROM {0} WHERE {1}";
// sql where condition like: Column1 = #Parameter1 AND Column2 = #Parameter2 etc.
var whereCondition = parameters.Select (p => String.Format("{0} = {1}", p.Key.Substring(1), p.Key)).Aggregate ((h, t) => String.Format("{0} AND {1}", h, t));
// build the complete condition
var sqlQuery = String.Format(whereQuery, tableName, whereCondition);
// debug
Console.WriteLine(sqlQuery);
// return the new dynamic query
return createSqlCommand(sqlQuery, parameters);
}
Now the creation of a SELECT command will look like this:
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
// specify only table name and arbitrary count of parameters
var getPersonSqlCommand = createSqlWhere("People", new Dictionary<String, Object>
{
{ "#Name", "J.D." },
{ "#Age", 30 }
});
SqlDataReader reader = getPersonSqlCommand.ExecuteReader();
The createSqlWhere method will return an initialized SqlCommand with the query:
SELECT * FROM People WHERE Name = #Name AND Age = #Age
The INSERT will also be short:
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
// specify only table name and arbitrary count of parameters
var addPersonSqlCommand = createSqlInsert("People", new Dictionary<String, Object>
{
{ "#Name", "Anonymous" },
{ "#Age", 25 },
{ "#Street", "Test" }
});
addPersonSqlCommand.ExecuteNonQuery();
The corresponding SQL command will look like this:
INSERT INTO People(Name, Age, Street) VALUES(#Name, #Age, #Street)
Other SQL commands like DELETE, UPDATE and so on can be created in the same way. New parameters should be added only in one place - in the dictionary.
Admittedly the initial effort is more than just writing one method, but it will pay off if the new methods are used more than once (a couple of times) - for example five parametrised selects and/or inserts on five different tables with different parameters, which is certainly always the case in small and average sized software projects.
Just create a method like :
public void unlimQuery(string query,params object[] args)
{
SqlConnection conn = new SqlConnection(_connectionString);
conn.Open();
string s =query;
SqlCommand cmd = new SqlCommand(s);
For(int i=0;i< args.Length;i++)
cmd.Parameters.Add("#param"+i, args[i]);
SqlDataReader reader = cmd.ExecuteReader();
}
Example :
unlimQuery("INSERT INTO CUSTOMERS(ID,NAME,AGE,ADRESS,COUNTRY) VALUES(#param0,#param1,#param2,#param3,#param4)",5,"Ali",27,"my City","England");
Explanation :
the params keyword in c# gives you the possibility to insert unlimited arguments of the indicated type, so the arguments added (5,"Ali",27,"my City","England") will be casted to an array of objects then passed to the Method
inside the method you'll get an array of objects, so for each object you create a parameter, his alias is #paramX where X is the index of the argument (in the params array), then sqlCommad will replace each alias by its value defined in the cmd.Parameters.Add("#param"+i, args[i]) clause
so #param0 => 5, .....
i think you just have to change this
cmd.Parameters.Add("#email", email);
to
cmd.Parameters.AddWithValue("#email", email);
I'm trying to parameterize a raw SQL query for an Oracle synonym (non-entity) in EF 4 and I am having some problems. Currently I am doing something like the code below, based on some examples that I saw:
string term="foo";
OracleParameter p = new OracleParameter("#param1", term);
object[] parameters = new object[] { p };
var model = db.Database.SqlQuery<ProjectTask>("SELECT * FROM (SELECT * FROM web_project_task_vw WHERE project_num like '%#param1%') WHERE rownum<=100", parameters).ToList();
Running this doesn't return any results. If I replace the parameter with something like
"SELECT * FROM web_project_task_vw WHERE project_num like '%"+term+"%'"
it returns the results I expect, but this is obviously a SQL injection risk.
Can anyone point me in the right direction for how parameters are supposed to work in EF 4 for an Oracle DB?
Thanks.
First, like Mohammed wrote, you need to prefix the parameter with ':', but not as you define it, just in the query.
Second, you are currently searching not for the value of the parameter but rather strings that contains the string #param1. So surround the value of the parameter with % and you should get a result.
So it should look something like this:
string term="foo";
OracleParameter p = new OracleParameter("param1", term);
object[] parameters = new object[] { p };
var model = db.Database.SqlQuery<ProjectTask>("SELECT * FROM (SELECT * FROM web_project_task_vw WHERE project_num like '%'||:param1||'%') WHERE rownum<=100", parameters).ToList();
Your p might have an incorrect parameter name; the name should be param1, not #param1. Your query is also incorrect; replace '%#param1%' with '%:param1%'.
That's what I tried & failed:
string sql = "... WHERE [personID] IN (#sqlIn) ...";
string sqlIn = "1,2,3,4,5";
SqlCeCommand cmd.Parameters.Add("#sqlIn", SqlDbType.NText).Value = sqlIn;
SqlCeDataAdapter da = new SqlCeDataAdapter(cmd);
da.Fill(ds); // > Error
Error details:
The ntext and image data types cannot be used in WHERE, HAVING, GROUP BY, ON, or IN clauses, except when these data types are used with the LIKE or IS NULL predicates.
Can't I pass all the IDs as one parameter? Should I add one by one all IDs?
P.S: Notice SqlCE
You can't parameterise that as a single parameter. Your query is doing an "in" on a single value, so is essentially:
... Where personId = '1,2,3,4,5'
(give or take a parameter). This is usually also an invalid or sub-optimal equality test, and certainly isn't what you were trying to query.
Options;
use raw concatenation: often involves a SQL injection risk, and allows poor query plan re-use
on full SQL server: use a UDF to split a single param
on full SQL server, use a TVP
add parameters dynamically, and add the various #param3 etc to the TSQL
The last is the most reliable, and "dapper-dot-net" has a feature built in to do this for you (since it is commonly needed):
int[] ids = ...
var rows = conn.Query<SomeType>(
#"... Where Id in #ids",
new { ids }).ToList();
This, when run via dapper-dot-net, will add a parameter per item in "ids", giving it the right value etc, and fixing the SQL so it executes, for example:
"... Where Id in (#ids0, #ids1, #ids2)"
(if there were 3 items in "ids")
You'll need to split the sqlIn string by comma, convert each to an integer, and build the IN statement manually.
string sqlIn = "1,2,3,4,5";
string inParams = sqlIn.Split(',');
List<string> paramNames = new List<string>();
for(var i = 0; i < inParams.Length; ++i){
string paramName = "#param" + i.ToString();
SqlCeCommand cmd.Parameters.Add(paramName, SqlDbType.Int).Value = int.Parse(inParams[i]);
paramNames.Add(paramName);
}
string sql = "... WHERE [personID] IN (" +
string.Join(",", paramNames) +
") ...";