Creating Datalayer in Class file

using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace DATAACCESS.SQL
{
public class DATALAYER:IDisposable
{
private IDbCommand cmd=new SqlCommand();
private string strConnectionString="";
private bool handleErrors=false;
private string strLastError="";
public DATALAYER()
{
ConnectionStringSettings objConnectionStringSettings = ConfigurationManager.ConnectionStrings["connect"];
strConnectionString = objConnectionStringSettings.ConnectionString;
SqlConnection cnn=new SqlConnection();
cnn.ConnectionString=strConnectionString;
cmd.Connection=cnn;
cmd.CommandType = CommandType.StoredProcedure;
}
public IDataReader ExecuteReader()
{ IDataReader reader=null;
try
{
this.Open();
reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
catch (Exception ex)
{
if (handleErrors)
strLastError = ex.Message;
else
throw;
}
return reader;
}
public IDataReader ExecuteReader(string commandtext)
{
IDataReader reader=null;
try
{
cmd.CommandText=commandtext;
reader=this.ExecuteReader();
}
catch(Exception ex)
{
if(handleErrors)
strLastError=ex.Message;
else
throw;
}
return reader;
}
public object ExecuteScalar()
{
object obj = null;
try
{ this.Open();
obj = cmd.ExecuteScalar();
this.Close();
}
catch (Exception ex)
{ if (handleErrors)
strLastError = ex.Message;
else
throw;
}
return obj;
}
public object ExecuteScalar(string commandtext)
{
object obj=null;
try
{ cmd.CommandText=commandtext;
obj= this.ExecuteScalar();
}
catch(Exception ex)
{ if(handleErrors)
strLastError=ex.Message;
else
throw;
}
return obj;
}

public int ExecuteNonQuery()
{
int i=-1;
try
{
this.Open();
i=cmd.ExecuteNonQuery();
this.Close();
}
catch(Exception ex)
{
if(handleErrors)
strLastError=ex.Message;
else
throw;
}
return i;
}
public int ExecuteNonQuery(string commandtext)
{
int i=-1;
try
{
cmd.CommandText=commandtext;
i=this.ExecuteNonQuery();
}
catch(Exception ex)
{
if(handleErrors)
strLastError=ex.Message;
else
throw;
}
return i;
}
public DataSet ExecuteDataSet()
{
SqlDataAdapter da=null;
DataSet ds=null;
try
{
da=new SqlDataAdapter();
da.SelectCommand=(SqlCommand)cmd;
ds=new DataSet();
da.Fill(ds);
}
catch(Exception ex)
{
if(handleErrors)
strLastError=ex.Message;
else
throw ex;
}
return ds;
}
public DataSet ExecuteDataSet(string commandtext)
{
DataSet ds=null;
try
{
cmd.CommandText=commandtext;
ds=this.ExecuteDataSet();
}
catch(Exception ex)
{
if(handleErrors)
strLastError=ex.Message;
else
throw;
}

return ds;
}

public string CommandText
{
get
{
return cmd.CommandText;
}
set
{
cmd.CommandText=value;
cmd.Parameters.Clear();
}
}

public IDataParameterCollection Parameters
{
get
{
return cmd.Parameters;
}
}

public void AddParameter(string paramname,object paramvalue)
{
SqlParameter param=new SqlParameter(paramname,paramvalue);
cmd.Parameters.Add(param);
}

public void AddParameter(IDataParameter param)
{
cmd.Parameters.Add(param);
}

public string ConnectionString
{
get
{
return strConnectionString;
}
set
{
strConnectionString=value;
}
}

private void Open()
{
cmd.Connection.Open();
}

private void Close()
{
cmd.Connection.Close();
}

public bool HandleExceptions
{
get
{
return handleErrors;
}
set
{
handleErrors=value;
}
}

public string LastError
{
get
{
return strLastError;
}
}

public void Dispose()
{
cmd.Dispose();
}
}

}