diff --git a/src/api/dotnet/Context.cs b/src/api/dotnet/Context.cs
index 07759b1fa..c06f58cbd 100644
--- a/src/api/dotnet/Context.cs
+++ b/src/api/dotnet/Context.cs
@@ -980,7 +980,8 @@ namespace Microsoft.Z3
             Debug.Assert(t != null);
             Debug.Assert(t.All(a => a != null));
             CheckContextMatch<BoolExpr>(t);
-            return new BoolExpr(this, Native.Z3_mk_and(nCtx, (uint)t.Count(), AST.EnumToNative(t)));
+            var ands = t.ToArray();
+            return new BoolExpr(this, Native.Z3_mk_and(nCtx, (uint)t.Count(), AST.ArrayToNative(ands)));
         }
 
         /// <summary>
@@ -1005,7 +1006,8 @@ namespace Microsoft.Z3
             Debug.Assert(t.All(a => a != null));
 
             CheckContextMatch(t);
-            return new BoolExpr(this, Native.Z3_mk_or(nCtx, (uint)t.Count(), AST.EnumToNative(t)));
+            var ts = t.ToArray();
+            return new BoolExpr(this, Native.Z3_mk_or(nCtx, (uint)ts.Length, AST.ArrayToNative(ts)));
         }
 
         #endregion
@@ -1032,7 +1034,8 @@ namespace Microsoft.Z3
             Debug.Assert(t.All(a => a != null));
 
             CheckContextMatch(t);
-            return (ArithExpr)Expr.Create(this, Native.Z3_mk_add(nCtx, (uint)t.Count(), AST.EnumToNative(t)));
+            var ts = t.ToArray();
+            return (ArithExpr)Expr.Create(this, Native.Z3_mk_add(nCtx, (uint)ts.Length, AST.ArrayToNative(ts)));
         }
 
         /// <summary>
@@ -1044,7 +1047,8 @@ namespace Microsoft.Z3
             Debug.Assert(t.All(a => a != null));
 
             CheckContextMatch<ArithExpr>(t);
-            return (ArithExpr)Expr.Create(this, Native.Z3_mk_mul(nCtx, (uint)t.Length, AST.ArrayToNative(t)));
+            var ts = t.ToArray();
+            return (ArithExpr)Expr.Create(this, Native.Z3_mk_mul(nCtx, (uint)ts.Length, AST.ArrayToNative(ts)));
         }
 
         /// <summary>
@@ -1056,7 +1060,8 @@ namespace Microsoft.Z3
             Debug.Assert(t.All(a => a != null));
 
             CheckContextMatch<ArithExpr>(t);
-            return (ArithExpr)Expr.Create(this, Native.Z3_mk_mul(nCtx, (uint)t.Count(), AST.EnumToNative(t)));
+            var ts = t.ToArray();
+            return (ArithExpr)Expr.Create(this, Native.Z3_mk_mul(nCtx, (uint)ts.Length, AST.ArrayToNative(ts)));
         }
 
         /// <summary>
@@ -2749,10 +2754,11 @@ namespace Microsoft.Z3
         /// </summary>
         public BoolExpr MkAtMost(IEnumerable<BoolExpr> args, uint k)
         {
-           Debug.Assert(args != null);
-           CheckContextMatch<BoolExpr>(args);
-           return new BoolExpr(this, Native.Z3_mk_atmost(nCtx, (uint) args.Count(),
-                                                          AST.EnumToNative(args), k));
+            Debug.Assert(args != null);
+            CheckContextMatch<BoolExpr>(args);
+            var ts = args.ToArray();
+            return new BoolExpr(this, Native.Z3_mk_atmost(nCtx, (uint) ts.Length,
+                                                          AST.ArrayToNative(ts), k));
         }
 
         /// <summary>
@@ -2760,10 +2766,11 @@ namespace Microsoft.Z3
         /// </summary>
         public BoolExpr MkAtLeast(IEnumerable<BoolExpr> args, uint k)
         {
-           Debug.Assert(args != null);
-           CheckContextMatch<BoolExpr>(args);
-           return new BoolExpr(this, Native.Z3_mk_atleast(nCtx, (uint) args.Count(),
-                                                          AST.EnumToNative(args), k));
+            Debug.Assert(args != null);
+            CheckContextMatch<BoolExpr>(args);
+            var ts = args.ToArray();
+            return new BoolExpr(this, Native.Z3_mk_atleast(nCtx, (uint) ts.Length,
+                                                          AST.ArrayToNative(ts), k));
         }
 
         /// <summary>
diff --git a/src/api/dotnet/Z3Object.cs b/src/api/dotnet/Z3Object.cs
index 9a61a0119..d25dfc25a 100644
--- a/src/api/dotnet/Z3Object.cs
+++ b/src/api/dotnet/Z3Object.cs
@@ -131,24 +131,10 @@ namespace Microsoft.Z3
             return an;
         }
 
-        internal static IntPtr[] EnumToNative<T>(IEnumerable<T> a) where T : Z3Object
-        {
-
-            if (a == null) return null;
-            IntPtr[] an = new IntPtr[a.Count()];
-            int i = 0;
-            foreach (var ai in a)
-            {
-                if (ai != null) an[i] = ai.NativeObject;
-                ++i;
-            }
-            return an;
-        }
-
         internal static uint ArrayLength(Z3Object[] a)
         {
             return (a == null)?0:(uint)a.Length;
         }
-        #endregion
+#endregion
     }
 }