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How to instantiate my business object without useing 'new' keyword.

Posted on 2010-11-10
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Last Modified: 2012-05-10
Below is my Fetch procedure, and this is in BusinessObjectFactory class -  this procedure takes two parameters - 1st parameter I want to send the type of class and other parameter is datarow/data table/ data set.

AssetToleranceBO is my class.

I want to instantiate my class 'AssetToleranceBO ' as below.
AssetToleranceBO assetTol = BusinessObjectFactory.Fetch(typeof(AssetToleranceBO), dr);

Now my question is how to define the parameters in Fetch method?
And also, entitiType.InvokeMember is expecting object[] args - how do I pass this, I want to pass either datarow / data table / data set
Can anyone help me?

public static object Fetch(object objBusiness, object criteria) 
        {
            Type entitiType = objBusiness.GetType();
            object obj = Activator.CreateInstance(entitiType);
            entitiType.InvokeMember("FetchData", BindingFlags.InvokeMethod, null, obj, criteria);
            return obj;
        }


        public class AssetToleranceBO : EntityBusinessBase
    {
        string _acctID;
        string _name;
        
               
        public string ID
        {
            get { return _acctID; }
            set { _acctID = value; }
        }
        
        public string CLASS
        {
            get { return _name; }
            set { _name = value; }
        }


        /// <summary>
        /// Fetches the data.
        /// </summary>
        /// <param name="criteria"></param>
        protected override void FetchData(DataRow criteria)
        { 
            _acctID = criteria["gpq_acct_id"].ToString();
            _name = criteria["acct_name"].ToString();
        }
}

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Question by:GouthamAnand
  • 4
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10 Comments
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 34105803
For starters the parameter type would be Type, as in:

     public static object Fetch(Type objBusiness, object criteria)
     {

     }

For the object[] parameter you would do:

     new object[] { yourParameterValue }
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LVL 20

Expert Comment

by:Daniel Van Der Werken
ID: 34106219
This worked for me but I had to use the "new" keyword in the method call.  Otherwise, the type was System.RunTimeType in the Fetch() method and I wasn't able to figure out why.  
 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Reflection;
using System.ServiceProcess;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            BusinessObjectFactory.AssetToleranceBO assetTol = (BusinessObjectFactory.AssetToleranceBO)BusinessObjectFactory.Fetch( new BusinessObjectFactory.AssetToleranceBO(), "Hello There" );
        }
    }

    public static class BusinessObjectFactory
    {
        static BusinessObjectFactory() { }

        public static object Fetch( object objBusiness, object criteria )
        {
            Type entityType = objBusiness.GetType();
            if ( !string.Equals( entityType.UnderlyingSystemType.Name, "RunTimeType", StringComparison.InvariantCultureIgnoreCase ) )
            {
                object obj = Activator.CreateInstance( entityType );
                entityType.InvokeMember( "FetchData", BindingFlags.InvokeMethod, null, obj, new object[] { criteria } );
                return obj;
            }
            else
            {
                return null;
            }
        }

        public class AssetToleranceBO
        {
            public AssetToleranceBO() { }

            public void FetchData( string someString )
            {
                MessageBox.Show( someString );
            }
        }
    }
}

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Author Comment

by:GouthamAnand
ID: 34106989
It says - No parameterless constructor defined for this object. - at object obj = Activator.CreateInstance( entityType );

I have defined parameterless constructor , but still it says - "No parameterless constructor defined for this object"
0
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LVL 20

Expert Comment

by:Daniel Van Der Werken
ID: 34107707
That's what happened to me when I initially tried it with

BusinessObjectFactory.AssetToleranceBO assetTol = (BusinessObjectFactory.AssetToleranceBO)BusinessObjectFactory.Fetch( typeof( BusinessObjectFactory.AssetToleranceBO ), "Hello There" );


instead of BusinessObjectFactory.AssetToleranceBO assetTol = (BusinessObjectFactory.AssetToleranceBO)BusinessObjectFactory.Fetch( new BusinessObjectFactory.AssetToleranceBO(), "Hello There" );

which are you trying.  Are you trying to use a Type parameter or an object parameter?  I could not get it to work with the Type parameter.  Basically, the type it resolves out to is System.RunTimeType which apparently has no default parameterless constructor.  
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LVL 7

Accepted Solution

by:
keustermans earned 500 total points
ID: 34119470
Try the Code below. You can create any kind of object with it.

 public class ObjectFactory
    {

        public static T CreateInstance<T>()
        {
            object instance = Activator.CreateInstance(typeof(T));
            return (T)instance;
        }


        public static T CreateInstance<T>(string invokeMember, object[] param)
        {
            Type type;
            type = typeof(T);
            object instance = Activator.CreateInstance(type);
            type.InvokeMember(invokeMember, BindingFlags.InvokeMethod, null, instance, param);
            return (T)instance;
        }
    }
0
 
LVL 7

Assisted Solution

by:keustermans
keustermans earned 500 total points
ID: 34119572
You can use the class as follows:

 public class TestClass
    {
        public string a { get; set; }
        public string b { get; set; }

        public string ab
        {
            get
            {
                return a + b;
            }
        }

        public void DoStuff(string arg1, string arg2)
        {
            a = arg1;
            b = arg2;
        }


    }

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            TestClass test = ObjectFactory.ObjectFactory.CreateInstance<TestClass>();
            test.a = "abc";
            test.b = "efg";

        }

        private void button2_Click(object sender, EventArgs e)
        {
            TestClass test = ObjectFactory.ObjectFactory.CreateInstance<TestClass>("DoStuff",new object[]{"Test","Class"});
        }
    }
0
 

Author Comment

by:GouthamAnand
ID: 34123103
This is what I am lookin for. Thanks alot.
But I am getting an error at entityType.InvokeMember. It says - "Method Business.Entities.AssetToleranceBO.FetchData' not found.

I have 'FetchData' method in AssetToleranceBO. I am not sure why it is not able to reach there.

please help me. Below is my code.
DataRow dr = AssetToleranceDA.FetchTolerance(assetID);

            AssetToleranceBO assetTol = BusinessObjectFactory.CreateBusinessObject<AssetToleranceBO>(typeof(AssetToleranceBO), dr); 


public static TObject CreateBusinessObject<TObject>(Type objBusiness, object criteria) 
        {
            Type entityType;

            entityType = typeof(TObject);

            object objInstance = Activator.CreateInstance(entityType, true);

            object[] param = new object[] { criteria };

            entityType.InvokeMember("FetchData", BindingFlags.InvokeMethod, null, objInstance, param);

            return (TObject)objInstance;
            
        }

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Author Closing Comment

by:GouthamAnand
ID: 34124264
Thanks a lot. This is exactly what I am looking for.
0
 
LVL 7

Expert Comment

by:keustermans
ID: 34126960
Hi,

It could be because your method si expecting a datarow and you are passing it an object.

Teh solution might be that you actualy put a datarow in the param object array.

I haven't tested this but it seems to be the obvious answer to me.
0
 
LVL 7

Expert Comment

by:keustermans
ID: 34126961
Oh by the way you might have to cast it back to Datarow in the the FetchData function.
0

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