泛型方法返回的委托<T>

Question

I have a method -

public T GetField<T> (string tableName, string fieldName)
{
    //Code
}

I need a delegate to hold this method. Not sure how to declare delegate for above method.

Now if I change my method

public T GetField<T> (string tableName, string fieldName, params IDbDataParameter[] parameters)
{
    //Code
}

public T Func<string,string ,string,IDbDataParameter[],T> GetFieldAction = GetField;// This is wrong

Any suggestion? Is it possible? Can I have a delegate which can hold generic return type method?

Is there any Func() workaround?

Answer 1

Based on your second method if you want to call that using c# Func , here is the code below.

public class Stackoverflow<T> 
{
    public  static Func<string,string,IDbDataParameter[],T> CallingFunc; 

    public static T GetField(string tableName, string fieldName, params IDbDataParameter[] parameters)
    {
        //Code
        return default(T);
    }        

}

public class MainProgram
{
    static void Main(string[] args)
    {
        Stackoverflow<int>.CallingFunc = Stackoverflow<int>.GetField;
        Stackoverflow<int>.CallingFunc("SampleTableName", "SampleField", new[]{
            new SqlParameter{DbType = DbType.Int32,Size = sizeof(Int32),ParameterName = "Id",Direction = ParameterDirection.Input},
            new SqlParameter{DbType = DbType.String,Size = 100,ParameterName = "name",Direction = ParameterDirection.Output}
        });

    }

}

Main method can't be call under generic class, so it's reside in other class. This workaround also can be possible using generic delegates like below

public class Stackoverflow<T> 
{

    public  delegate T CallingDelegate(string tableName, string fieldName, params IDbDataParameter[] parameters); 

    public static T GetField(string tableName, string fieldName, params IDbDataParameter[] parameters)
    {
        //Code
        return default(T);
    }        

}

public class MainProgram
{
    static void Main(string[] args)
    {
        Stackoverflow<int>.CallingDelegate del = Stackoverflow<int>.GetField;
        del("SampleTableName", "SampleField", new[]{
            new SqlParameter{DbType = DbType.Int32,Size = sizeof(Int32),ParameterName = "Id",Direction = ParameterDirection.Input},
            new SqlParameter{DbType = DbType.String,Size = 100,ParameterName = "name",Direction = ParameterDirection.Output}
        });

    }

}

Answer 2

Why not Func<string, string, T> ?

Or, alternatively, if you don't want to use Func :

delegate T MyDelegate<T>(string tableName, string fieldName);

EDIT: Example code which addresses your comment:

delegate T MyDelegate<T>(string tableName, string fieldName, params IDbDataParameter[] parameters);

private T GetField<T>(string tableName, string fieldName, params IDbDataParameter[] parameters)
{
  return default(T);
}

void Main()
{
  MyDelegate<int> del = this.GetField<int>;
}