Linq query to get data from array of objects c#

Question

public struct Parameter 
{
    public Parameter(string name, string type, string parenttype)  
    {        
        this.Name = name;
        this.Type = type;
        this.ParentType = parenttype;        
    }
    public string Name;
    public string Type;
    public string ParentType;
}

Following values are stored in the array of Parameter:

Name        Type                 ParentType
-------------------------------------------------------
composite   CompositeType        
isThisTest  boolean              
BoolValue   boolean              CompositeType
StringValue string               CompositeType
AnotherType AnotherCompositeType CompositeType
account     string               AnotherCompositeType
startdate   date                 AnotherCompositeType

I want to read this to build an xml. something like:

<composite>
    <BoolValue>boolean</BoolValue>
    <StringValue>string</StringValue>
    <AnotherType>
        <account>string</account>
        <startdate>date</startdate>
    </AnotherType>    
<composite>
<isThisTest>boolean</isThisTest>

I am using the following logic to read the values:

foreach (Parameter parameter in parameters)
{
    sb.Append("        <" + parameter.Name + ">");
    //HERE: need to check parenttype and get all it's child elements
    //
    sb.Append("</" + parameter.Name + ">" + CrLf);
}

Is there a simpler way to read the array to get the parents and thier child? May be using LINQ? I still on .Net 3.5. Appreciate any suggestions with example code :)

Is the depth of the hierarchy fixed or variable? One algorithm expecting a depth of two could be much faster than one with an arbitrary depth. — Norman H
– Norman H, Commented Mar 28, 2011 at 13:34
Linkgoron, this is an existing code that I am trying to work on. Will it make major difference in using class? And not sure about yout second part of your question. How to do that and what am I gonna achieve? — Sri Reddy
– Sri Reddy, Commented Mar 28, 2011 at 14:10

Mongus Pong · Accepted Answer · 2011-03-28 16:14:25Z

5

You could write a little recursive method to deal with this :

IEnumerable<XElement> GetChildren ( string rootType, List<Parameter> parameters )
{
    return from p in parameters
        where p.ParentType == rootType
        let children = GetChildren ( p.Type, parameters )
        select  children.Count() == 0 ? 
            new XElement ( p.Name, p.Type ) :
            new XElement ( p.Name, children );
}

Each call builds up an Enumerable of XElements which contains the parameters whose parent has the passed in type. The select recurses into the method again finding the children for each Element.

Note that this does assume that the data is correctly formed. If two parameters has eachother as a parent you will get a Stack Overflow.

The magic is in the XElements class (Linq to Xml) that accepts enumerables of XElements to build up the tree like Xml structure.

The first call, pass null (or use default parameters if using C# 4) as the rootType. Use like :

void Main()
{
    var parameters = new List<Parameter> {
        new Parameter {Name = "composite", Type = "CompositeType" },
        new Parameter {Name = "isThisTest", Type = "boolean" },
        new Parameter {Name = "BoolValue", Type = "boolean", ParentType = "CompositeType" },
        new Parameter {Name = "StringValue", Type = "string", ParentType = "CompositeType" },
        new Parameter {Name = "AnotherType", Type = "AnotherCompositeType", ParentType = "CompositeType" },
        new Parameter {Name = "account", Type = "string", ParentType = "AnotherCompositeType" },
        new Parameter {Name = "startdate", Type = "date", ParentType = "AnotherCompositeType" }
    };

    foreach ( var r in GetChildren ( null, parameters ) )
    {
        Console.WriteLine ( r );
    }

}

Output :

<composite>
  <BoolValue>boolean</BoolValue>
  <StringValue>string</StringValue>
  <AnotherType>
    <account>string</account>
    <startdate>date</startdate>
  </AnotherType>
</composite> 
<isThisTest>boolean</isThisTest>

Edit

In response to your comment, XElement gives you two options for outputting as a string.

ToString() will output formatted Xml.

ToString(SaveOptions) allows you to specify formatted or unformatted output as well as ommitting duplicate namespaces.

I'm sure you could probably adapt the solution to use StringBuilder if you really had to, although it probably wouldn't be as elegant..

edited Mar 28, 2011 at 16:14

answered Mar 28, 2011 at 14:46

Mongus Pong

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6 Comments

Sri Reddy Over a year ago

Mongus, this is an ultimate solution. Linq is such an effective way to code, couple of lines and wooh!! Thanks for the wonderful solution. One question though, does XElement do the formatting of the data (indentation?) and if store the above result to StringBuilder can I retain the formatting?

Sri Reddy Over a year ago

Mongus, if I want to go with formatted xml using ToString(), where exactly I should use it and how?

Mongus Pong Over a year ago

I'm not exactly sure what you mean - you would use it wherever you need to use the string representation. Instead of wherever you were going to use your sb variable, you use the r variable in my example (r is a bad name for the variable - you should rename it to something more useful!)

Mongus Pong Over a year ago

Note that in this example the first call to GetChildren will return two XElement's. One contains the "composite" xml and the other contains the "isThisTest" xml. If you wanted to combine it all into one xml you could do : var xml = new XElement("root", GetChildren ( null, parameters ) ); Then use xml.ToString() wherever you need.

Mongus Pong Over a year ago

Without knowing the full details all I can really say is - if it works it can't be bad!

|

Joel C · Accepted Answer · 2011-03-28 16:00:37Z

1

It looks like you want to use a recursive method, something like:

string GetChildren(Parameter param, string indent)
{
    StringBuilder sb = new StringBuilder();
    if (HasChildren(param))
    {
        sb.AppendFormat("{0}<{1}>{2}", indent, param.Name, Environment.NewLine);
        foreach (Parameter child in parameters.Where(p => p.ParentType == param.Type))
        {
            sb.Append(GetChildren(child, indent + "   "));
        }
        sb.AppendFormat("{0}</{1}>{2}", indent, param.Name, Environment.NewLine);
    }
    else
    {
        sb.AppendFormat("{0}<{1}>{2}</{1}>{3}", indent, param.Name, param.Type, Environment.NewLine);
    }
    return sb.ToString();
}

The method that looks to see whether a Parameter has child nodes would look like:

bool HasChildren(Parameter param)
{
    return parameters.Any(p => p.ParentType == param.Type);
}

The collection parameters could be defined as an IEnumerable<Parameter> and could be implemented using a List<Parameter>.

answered Mar 28, 2011 at 16:00

Joel C

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1 Comment

Sri Reddy Over a year ago

thanks joel for another solution. I liked Mongus's solution at this time.

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