No mapping exists from object type System.Collections.Generic.List when executing stored proc with parameters in EF 4.3

问题

Lately I've been working on stored procedure and encountered 1 strange problem.

First, I was able to successfully call a stored procedure from the database via:

IList<XXXViewModel> XXXList = _context.Database.SqlQuery("spXXX").ToList();

But when I needed to pass parameters it failed:

var parameters = new List<SqlParameter>();
parameters.Add(new SqlParameter("param1", param1Value));
parameters.Add(new SqlParameter("param2", param2Value));
IList<XXXViewModel> XXXList =
_context.Database.SqlQuery<XXXViewModel>("spXXX @param1, @param2", parameters).ToList();

And I got the ff, error:

No mapping exists from object type System.Collections.Generic.List`1[[System.Data.SqlClient.SqlParameter, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] to a known managed provider native type.

Note that I've also tried:

_context.Database.ExecuteSqlCommand<EXEC XXXViewModel>("spXXX @param1, @param2", parameters).ToList();

But got the same result :-(.

Also I've tried calling, by specifying each of the parameters:

IList<XXXResult> query = Context.Database.SqlQuery<XXXResult>("SP @paramA, @paramB, @paramC", new SqlParameter("paramA", "A"), new SqlParameter("paramB", "B"), new SqlParameter("paramC", "C")).ToList();

Anyone has any idea?

回答1:

You need to pass each parameter to the method (ie You can't pass a list)

IList<XXXViewModel> XXXList =
     _context.Database.SqlQuery<XXXViewModel>("spXXX @param1, @param2", 
     new SqlParameter("param1", param1Value), 
     new SqlParameter("param2", param2Value)).ToList();

回答2:

In case someone else comes across this...

I created the parameters as a List and then in the SqlQuery call I passed it with a .ToArray(). Worked for me. Here's the modified code below...

var parameters = new List<object>(); 
parameters.Add(new SqlParameter("param1", param1Value)); 
parameters.Add(new SqlParameter("param2", param2Value)); 
IList<XXXViewModel> XXXList = 
_context.Database.SqlQuery<XXXViewModel>("spXXX @param1, @param2", parameters.ToArray()).ToList(); 

回答3:

The solution for this problem (in my case was)

 var stuff = db.Database.SqlQuery<SomeEntityType>(query, parms);

Where query was a string that had parameters inserted such as @Name etc. The parms variable was a List of SQLParameters. SQL doesn't like generic lists....

SQL must have an array of SQLParameters sent as and object[] and not a list of generic type.

var stuff = db.Database.SqlQuery<SomeEntityType>(query, parms.ToArray());

回答4:

In my case parameter's SQL type and handling null values solved this problem. It was throwing same exception No mapping exists from object type System.RuntimeType to a known managed provider native type. for this also

var parameter1 = new SqlParameter("parameter1", typeof(string));
var parameter2 = new SqlParameter("parameter2", typeof(string));
var parameter3 = new SqlParameter("parameter3", typeof(string));

parameter1.Value = string.IsNullOrEmpty(parameter1Value) ? (object)DBNull.Value : parameter1Value;
parameter2.Value = string.IsNullOrEmpty(parameter2Value) ? (object)DBNull.Value : parameter2Value;
parameter3.Value = string.IsNullOrEmpty(parameter3Value) ? (object)DBNull.Value : parameter3Value;

http://karim-medany.blogspot.ae/2014/02/no-mapping-exists-from-object-type.html

回答5:

didn't state SQL Server version, but Erland Sommarskog has an article on how to use Table-Valued Parameters in SQL Server and .NET.

http://www.sommarskog.se/arrays-in-sql-2008.html

Able to pass a variable amount of arguments from client using a single parameter.

回答6:

If the stored procedure is only for update/insert, the following can be used as well.

string cmd = Constants.StoredProcs.usp_AddRoles.ToString() + " @userId, @roleIdList";
int result = db.Database
                        .ExecuteSqlCommand
                        (
                           cmd,
                           new SqlParameter("@userId", userId),
                           new SqlParameter("@roleIdList", roleId)
                        );

回答7:

You can also use string.Format to pass parameters to a stored procedure

string command = string.Format("EXEC spXXX {0},{1}", param1Value, param2Value);
IList<XXXViewModel> XXXList = 
  _context.Database.SqlQuery<XXXViewModel>(command).ToList();

来源：https://stackoverflow.com/questions/9149919/no-mapping-exists-from-object-type-system-collections-generic-list-when-executin