Func Delegate In C#
Func Delegate in C#:
·        A delegate is a type safe mechanism, one of the important and built -in delegate or a built-in generic delegate is “Func Delegate”.
·        When ever we define a delegate then we should be analyzing the requirement whether it must have return type, either one or multiple parameter based on the method defined.
·        We can say func delegate as Function delegate which means method with return type and zero to one or more parameter.
·        Func Delegate has 17 overloaded methods i.e. Method with no parameter to method takes 16 parameters.
·        Func Delegate has been designed to support the method has return type.
·        Func Delegate has been designed to work with Anonymous type as well as lambda expressions.
·        Func Delegate has been initiated with 3.0.
Syntax:
[Access Modifier] [Func<No Of Input parameter(Optional) + One Output Parameter(Last One)>] [Name of Delegate]
Example,


        #region Func Delegate In c#

        public class FuncDelegateDemo
        {
            DelegateEnum _funcDelegateTypeEnum = default(DelegateEnum);

            string Fname = "DotNet";

            string Lname = "360World";

            StringBuilder _stringBuilder = new StringBuilder();


            // Here  Func Delegate has been defined without Parameter
            public Func<string> FuncDelegateWithoutParameter;

            // Here  Func Delegate has been defined with one Parameter
            public Func<string, string> FuncDelegateWithParameter;


            public enum DelegateEnum
            {
                FuncwithoutParameter = 1,
                FuncwithParameter = 2,
            }

            public FuncDelegateDemo(DelegateEnum delegateEnum,ref StringBuilder stringBuilder)
            {
                _funcDelegateTypeEnum = delegateEnum;

                _stringBuilder = stringBuilder;

                FuncDelegateWithoutParameter = MethodOne;

                FuncDelegateWithParameter = MethodTwo;

                callingMethod();
            }

            /// <summary>
            /// Method With Zero Parameter
            /// </summary>
            /// <returns></returns>

            private string MethodOne()
            {
                return $"{Fname + Lname} - Returned From FuncWithoutParameter";
            }

            /// <summary>
            /// Method with One Parameter
            /// </summary>
            /// <param name="methodName"></param>
            /// <returns></returns>
            private string MethodTwo(string methodName)
            {
                return $"{Fname + Lname}- Returned From {methodName}";
            }

            /// <summary>
            /// callingMethod
            /// </summary>
            private void callingMethod()
            {

                string respone = string.Empty;

                switch (_funcDelegateTypeEnum)
                {
                    case DelegateEnum.FuncwithoutParameter:

                        _stringBuilder.AppendLine("==============Method Calling FUNC without Parameter  Starts===============");

                        // Calling method one with func Delegates with zero parameter
                        respone = FuncDelegateWithoutParameter();

                        _stringBuilder.AppendLine($"Output  - {respone}");

                        _stringBuilder.AppendLine("==============Method Calling FUNC without Parameter  Ends===============");

                        break;
                    case DelegateEnum.FuncwithParameter:

                        _stringBuilder.AppendLine("==============Method Calling FUNC with Parameter  Starts===============");

                        // Calling methodTwo with func Delegates with one parameter
                        respone = FuncDelegateWithParameter("FuncDelegateWithParameter");

                        _stringBuilder.AppendLine($"Output  - {respone}");

                        _stringBuilder.AppendLine("==============Method Calling FUNC with Parameter  Ends===============");

                        break;
                }


            }
        }

        /// <summary>
        /// funcDelegateBtn_Click
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void funcDelegateBtn_Click(object sender, EventArgs e)
        {
            StringBuilder stringBuilder = new StringBuilder();

            // Calling for without parameter - FUNC
            FuncDelegateDemo funcDelegateDemo = new FuncDelegateDemo(FuncDelegateDemo.DelegateEnum.FuncwithoutParameter, ref stringBuilder);

            // Reinitialized  - Calling for with parameter - FUNC
            funcDelegateDemo = new FuncDelegateDemo(FuncDelegateDemo.DelegateEnum.FuncwithParameter, ref stringBuilder);
           
            //prinitng values
            MessageBox.Show(stringBuilder.ToString());

        }

        #endregion
Output

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