Update and fix Nep17 template (#891)

- Use _deploy to set the owner
- Fix compilation errors

src/Neo.SmartContract.Template/templates/neocontractnep17/Contract1.cs

@@ -1,5 +1,4 @@
 using Neo;
-using Neo.SmartContract;
 using Neo.SmartContract.Framework;
 using Neo.SmartContract.Framework.Attributes;
 using Neo.SmartContract.Framework.Native;
@@ -25,19 +24,10 @@ public class Contract1 : Nep17Token
 
         private const byte Prefix_Owner = 0xff;
 
-        // TODO: Replace it with your own address.
-        [InitialValue("<Your Address Here>", Neo.SmartContract.ContractParameterType.Hash160)]
-        private static readonly UInt160 InitialOwner = default;
-
         [Safe]
         public static UInt160 GetOwner()
         {
-            var currentOwner = Storage.Get(new[] { Prefix_Owner });
-
-            if (currentOwner == null)
-                return InitialOwner;
-
-            return (UInt160)currentOwner;
+            return (UInt160)Storage.Get(new[] { Prefix_Owner });
         }
 
         private static bool IsOwner() =>
@@ -52,24 +42,22 @@ public static void SetOwner(UInt160 newOwner)
         {
             if (IsOwner() == false)
                 throw new InvalidOperationException("No Authorization!");
-            if (newOwner != null && newOwner.IsValid)
-            {
-                Storage.Put(new[] { Prefix_Owner }, newOwner);
-                OnSetOwner(newOwner);
-            }
+
+            ExecutionEngine.Assert(newOwner.IsValid && !newOwner.IsZero, "owner must be valid");
+
+            Storage.Put(new[] { Prefix_Owner }, newOwner);
+            OnSetOwner(newOwner);
         }
 
         #endregion
 
         #region NEP17
 
-        // NOTE: Valid Range 0-31
-        [Safe]
-        public override byte Decimals() => 8;
-
         // TODO: Replace "EXAMPLE" with a short name all UPPERCASE 3-8 characters
-        [Safe]
-        public override string Symbol() => "EXAMPLE";
+        public override string Symbol { [Safe] get => "EXAMPLE"; }
+
+        // NOTE: Valid Range 0-31
+        public override byte Decimals { [Safe] get => 8; }
 
         public static new void Burn(UInt160 account, BigInteger amount)
         {
@@ -141,6 +129,16 @@ public static void _deploy(object data, bool update)
                 return;
             }
 
+            // Init method, you must deploy the contract with the owner as an argument, or it will take the sender
+            if (data is null) data = Runtime.Transaction.Sender;
+
+            UInt160 initialOwner = (UInt160)data;
+
+            ExecutionEngine.Assert(initialOwner.IsValid && !initialOwner.IsZero, "owner must exists");
+
+            Storage.Put(new[] { Prefix_Owner }, initialOwner);
+            OnSetOwner(initialOwner);
+
             // This will be executed during deploy
             Storage.Put(Storage.CurrentContext, "Hello", "World");
         }