Generic Method - Iterate through a generic type

Mark Maguire

I have a generic method which I pass an object of a certain type. This object incorporates IEnumerable and IEnumerator in order to allow iteration using foreach, however when I try to iterate it which in the generic method i gives me this error >> "foreach statement cannot operate on variables of type 'T' because 'T' does not contain a public definition for 'GetEnumerator''

Here is my code:

        private bool GenericSummaryResultComparison(string szRiskRecordFilePath, string szResultSetSchemaFilePath) where T : class
        {
            try
            {
                T oRiskRecord;

//Read in the result files.
oRiskRecord = SerializationMethods.DeserializeIt(szResultFilePath1, szResultSetSchemaFilePath);

                foreach (T o in oRiskRecord)
                {
                    // actions
                }

                return true;
            }
            catch (Exception ex)
            {
                throw new ArgumentException(ex.Message, ex.InnerException);
            }
        }

How can I get this iteration to work?

Thanks

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Praneeth Kumar15y ago
Did you try putting a break point in line below and check whether oRiskRecord is of type RiskRecord itself?

oRiskRecord = SerializationMethods.DeserializeIt(szResultFilePath1, szResultSetSchemaFilePath);
Mark Maguire15y ago
Apologies, I do incorporate the GetEnumerator. I accidentally did not include it.
It still has the problem even with the GetEnumerator code in it.

Thanks
Mark

Praneeth Kumar15y ago

Try this

 public class RiskRecord : ISerializable, IEnumerable 
    {
        #region Private IEnumerable declarations
 
        public RiskRecord[] oRiskRecordElements;
 
        #endregion

        public RiskRecord(RiskRecord[] oArray)
        {
            //No contructor code required.
            //NOTE: This contructor is required for serialization.
            oRiskRecordElements = oArray;
        }

    #region IEnumerable Members
     public IEnumerator GetEnumerator()
     {
         return (IEnumerator)new RiskRecordEnumerator(this);
     }
     #endregion

    public class RiskRecordEnumerator : IEnumerator
    {
        private int iPos = -1;
        private RiskRecord oRiskRecord;
 
        public RiskRecordEnumerator(RiskRecord oRiskRecord)
        {
            try
            {
                this.oRiskRecord = oRiskRecord;
            }
            catch (Exception ex)
            {
                throw new ArgumentException(ex.Message, ex.InnerException);
            }
        }
 
        //Declare the MoveNext method as required by the IEnumerator.
        public bool MoveNext()
        {
            try
            {
                if (iPos < oRiskRecord.oRiskRecordElements.Length - 1)
                {
                    iPos++;
                    return true;
                }
                else
                {
                    return false;
                }
            }
            catch (Exception ex)
            {
                throw new ArgumentException(ex.Message, ex.InnerException);
            }
        }
 
        //Declare the Reset method required by the IEnumerator
        public void Reset()
        {
            iPos = -1;
        }
 
        //Declare the Current property required by the IEnumerator
        public object Current
        {
            get
            {
                return oRiskRecord.oRiskRecordElements[iPos];
            }
        }
    }

Mark Maguire15y ago

Please see this log: http://www.c-sharpcorner.com/Forums/Thread/126443/iterate-an-object-in-a-generic-method.aspx

I accidently submitted this one before i completed it.

Let me know if that helps you in anyway.

The code below is from the class object representing RiskRecord, it shows that I have incorporated IEnumerable and IEnumerator (NOTE: I have removed data properties from the RiskRecord class as it would be too long to include them).

    public class RiskRecord : ISerializable, IEnumerable 
    {
        #region Private IEnumerable declarations
 
        public RiskRecord[] oRiskRecordElements;
 
        #endregion

        public RiskRecord(RiskRecord[] oArray)
        {
            //No contructor code required.
            //NOTE: This contructor is required for serialization.
            oRiskRecordElements = oArray;
        }

    public class RiskRecordEnumerator : IEnumerator
    {
        private int iPos = -1;
        private RiskRecord oRiskRecord;
 
        public RiskRecordEnumerator(RiskRecord oRiskRecord)
        {
            try
            {
                this.oRiskRecord = oRiskRecord;
            }
            catch (Exception ex)
            {
                throw new ArgumentException(ex.Message, ex.InnerException);
            }
        }
 
        //Declare the MoveNext method as required by the IEnumerator.
        public bool MoveNext()
        {
            try
            {
                if (iPos < oRiskRecord.oRiskRecordElements.Length - 1)
                {
                    iPos++;
                    return true;
                }
                else
                {
                    return false;
                }
            }
            catch (Exception ex)
            {
                throw new ArgumentException(ex.Message, ex.InnerException);
            }
        }
 
        //Declare the Reset method required by the IEnumerator
        public void Reset()
        {
            iPos = -1;
        }
 
        //Declare the Current property required by the IEnumerator
        public object Current
        {
            get
            {
                return oRiskRecord.oRiskRecordElements[iPos];
            }
        }
    }

Thanks
Mark

Praneeth Kumar15y ago
      foreach (T o in oRiskRecord)
                {
                    // actions
                }

In this line it throws error because oRiskRecord is not of type collection which is implementing IEnumerator. Can you post any sample project if you have?

Regards,
Praneeth
Jaganathan Bantheswaran15y ago
Hi,

Instead of T use "var".