send parameter to windows azure mobile server script in c# for Windows 8 Store app - sql

Question

I modified the "Read" operation on my Windows Azure Mobile Services Preview table (named "Item") as follows:
Javascript:
function read(query, user, request)
{
var howRead;
if(howRead == "unique")
{
var sqlUnique = "SELECT DISTINCT ? FROM Item WHERE qProjectCode = ?";
mssql.query(sqlUnique)
request.execute();
}
else if (howRead == "column")
{
var sqlColumn = "SELECT ? FROM Item WHERE qProjectCode = ?";
mssql.query(sqlColumn)
request.execute();
}
else if (howRead == "all")
{
var sqlAll = "SELECT * FROM Item WHERE qProjectCode = ?";
mssql.query(sqlAll)
request.execute();
}
}
This simply species when I want a unique list of a single column's values returned, all items in a single column, or all columns, respectively, all while limiting the read to those records with a given project code.
Right now, this works in C#, but scans the entire table (with other project codes) and always returns all columns. This is inherently inefficient.
c#
var client = new MobileServiceClient("[https path", "[key]");
var table = client.GetTable<Item>();
var query1 = table.Where(w => w.QProjectCode == qgv.projCode && w.QRecord == (int)lbRecord.Items[uStartRecordIndex]);
var query1Enum = await query1.ToEnumerableAsync();
foreach (var i in query1Enum)
{
// process data
}
How do I alter the c# code to deal with the Javascript code? Feel free to critique the overall approach, since I am not a great programmer and can always use advice!
Thanks

Answer 1

A few things:
In your server code, the mssql calls are not doing anything (useful). If you want to get their results, you need to pass a callback (the call is asynchronous) to it.
Most of your scenarios can be accomplished at the client side. The only for which you'll need server code is the one with the DISTINCT modifier.
For that scenario, you'll need to pass a custom parameter to the server script. You can use the WithParameters method in the MobileServiceTableQuery<T> object to define parameters to pass to the service.
Assuming this data class:
public class Item
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string Other { get; set; }
public string ProjectCode { get; set; }
}
The code below can be used to accomplish the scenarios 2 and 3 at the client side only (no script needed at the server side). The other one will need some script, which I'll cover later.
Task<IEnumerable<string>> ReadingByColumn(IMobileServiceTable<Item> table, string projectCode)
{
return table
.Where(i => i.ProjectCode == projectCode)
.Select(i => i.Name)
.ToEnumerableAsync();
}
Task<IEnumerable<Item>> ReadingAll(IMobileServiceTable<Item> table, string projectCode)
{
return table.Where(i => i.ProjectCode == projectCode).ToEnumerableAsync();
}
Task<IEnumerable<string>> ReadingByColumnUnique(IMobileServiceTable<Item> table, string projectCode)
{
var dict = new Dictionary<string, string>
{
{ "howRead", "unique" },
{ "projectCode", projectCode },
{ "column", "Name" },
};
return table
.Select(i => i.Name)
.WithParameters(dict)
.ToEnumerableAsync();
}
Now, to support the last method (which takes the parameters, we'll need to do this on the server script:
function read(query, user, request)
{
var howRead = request.parameters.howRead;
if (howRead) {
if (howRead === 'unique') {
var column = request.parameters.column; // WARNING: CHECK FOR SQL INJECTION HERE!!! DO NOT USE THIS IN PRODUCTION!!!
var sqlUnique = 'SELECT DISTINCT ' + column + ' FROM Item WHERE ProjectCode = ?';
mssql.query(sqlUnique, [request.parameters.projectCode], {
success: function(distinctColumns) {
var results = distinctColumns.map(function(item) {
var result = [];
result[column] = item; // mapping to the object shape
return result;
});
request.respond(statusCodes.OK, results);
}
});
} else {
request.respond(statusCodes.BAD_REQUEST, {error: 'Script does not support option ' + howRead});
}
} else {
// no server-side action needed
request.execute();
}
}