diff --git a/src/api/dotnet/ArrayExpr.cs b/src/api/dotnet/ArrayExpr.cs
index 5fc27d253..513696f12 100644
--- a/src/api/dotnet/ArrayExpr.cs
+++ b/src/api/dotnet/ArrayExpr.cs
@@ -39,11 +39,13 @@ namespace Microsoft.Z3
         }
         #endregion	
 
+        /// <summary> Single argument select </summary>
         public Expr this[Expr index] 
         {
             get { return Context.MkSelect(this, index); }
         }
 
+        /// <summary> Multi argument select </summary>
         public Expr this[IEnumerable<Expr> index] 
         {
             get { return Context.MkSelect(this, index.ToArray()); }
diff --git a/src/api/dotnet/SeqExpr.cs b/src/api/dotnet/SeqExpr.cs
index 1544d630f..227556391 100644
--- a/src/api/dotnet/SeqExpr.cs
+++ b/src/api/dotnet/SeqExpr.cs
@@ -39,6 +39,7 @@ namespace Microsoft.Z3
         }
         #endregion
 
+        /// <summary> Access the nth element of a sequence </summary>
         public Expr this[Expr index] 
         {
             get { return Context.MkNth(this, index); }