more work on modelbuilder C#; fix doc on modelbuilder java

ortools/java/com/google/ortools/modelbuilder/LinearConstraint.java

@@ -35,39 +35,39 @@ public ModelBuilderHelper getHelper() {
     return helper;
   }
 
-  /** Returns the lower bound of the variable. */
+  /** Returns the lower bound of the constraint. */
   public double getLowerBound() {
     return helper.getConstraintLowerBound(index);
   }
 
-  /** Returns the lower bound of the variable. */
+  /** Returns the lower bound of the constraint. */
   public void setLowerBound(double lb) {
     helper.setConstraintLowerBound(index, lb);
   }
 
-  /** Returns the upper bound of the variable. */
+  /** Returns the upper bound of the constraint. */
   public double getUpperBound() {
     return helper.getConstraintUpperBound(index);
   }
 
-  /** Returns the upper bound of the variable. */
+  /** Returns the upper bound of the constraint. */
   public void setUpperBound(double ub) {
     helper.setConstraintUpperBound(index, ub);
   }
 
-  /** Returns the name of the variable given upon creation. */
+  /** Returns the name of the constraint given upon creation. */
   public String getName() {
     return helper.getConstraintName(index);
   }
 
-  // Sets the name of the variable. */
+  // Sets the name of the constraint. */
   public void setName(String name) {
     helper.setConstraintName(index, name);
   }
 
   // Adds var * coeff to the constraint.
-  public void addTerm(Variable var, double coeff) {
-    helper.addConstraintTerm(index, var.getIndex(), coeff);
+  public void addTerm(Variable v, double coeff) {
+    helper.addConstraintTerm(index, v.getIndex(), coeff);
   }
 
   /** Inline setter */

ortools/linear_solver/csharp/ModelBuilderConstraint.cs

@@ -0,0 +1,89 @@
+// Copyright 2010-2022 Google LLC
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+namespace Google.OrTools.ModelBuilder
+{
+  using Google.OrTools.Util;
+  using System;
+  using System.Collections;
+  using System.Collections.Generic;
+  using System.Linq;
+  using System.Runtime.CompilerServices;
+  using Google.Protobuf.Collections;
+
+  /** Wrapper around a linear constraint stored in the ModelBuilderHelper instance. */
+  public class LinearConstraint
+  {
+    public LinearConstraint(ModelBuilderHelper helper)
+    {
+      helper_ = helper;
+      index_ = helper_.AddLinearConstraint();
+    }
+
+    LinearConstraint(ModelBuilderHelper helper, int index)
+    {
+      helper_ = helper;
+      index_ = index;
+    }
+
+    /** Returns the index of the constraint in the model. */
+    public int Index
+    {
+      get { return index_; }
+    }
+
+    /** Returns the constraint builder. */
+    public ModelBuilderHelper Helper
+    {
+      get { return helper_; }
+    }
+
+    /** The lower bound of the constraint. */
+    public double LowerBound
+    {
+      get { return helper_.ConstraintLowerBound(index_); }
+      set { helper_.SetConstraintLowerBound(index_, value); }
+    }
+
+    /** The upper bound of the constraint. */
+    public double UpperBound
+    {
+      get { return helper_.ConstraintUpperBound(index_); }
+      set { helper_.SetConstraintUpperBound(index_, value); }
+    }
+
+    /** The name of the variable given upon creation. */
+    public String Name
+    {
+      get { return helper_.ConstraintName(index_); }
+      set { helper_.SetConstraintName(index_, value); }
+    }
+
+    // Adds var * coeff to the constraint.
+    public void AddTerm(Variable var, double coeff)
+    {
+      helper_.AddConstraintTerm(index_, var.Index, coeff);
+    }
+
+    /** Inline setter */
+    public LinearConstraint WithName(String name)
+    {
+      Name = name;
+      return this;
+    }
+
+    private readonly int index_;
+    private ModelBuilderHelper helper_;
+  }
+
+} // namespace Google.OrTools.ModelBuilder

ortools/linear_solver/csharp/ModelBuilderExpr.cs

@@ -515,13 +515,19 @@ public double LowerBound
         get {
             return helper_.VarLowerBound(index_);
         }
+        set {
+            helper_.SetVarLowerBound(index_, value);
+        }
     }
 
     public double UpperBound
     {
         get {
             return helper_.VarUpperBound(index_);
         }
+        set {
+            helper_.SetVarUpperBound(index_, value);
+        }
     }    
 
     public override string ToString()