Added dim to HessianFormat and started adding Hessian to call_highs_f…

…rom_csharp.cs

examples/call_highs_from_csharp.cs

@@ -6,6 +6,7 @@
 
 class Program {
    static void Main(string[] args) {
+       // Test with an LP
       double[] cc = {1, -2};
       double[] cl = {0, 0};
       double[] cu = {10, 10};
@@ -43,5 +44,13 @@ static void Main(string[] args) {
       for (int i=0; i<sol.colvalue.Length; i++) {
          Console.WriteLine("x" + i + " = " + sol.colvalue[i] + " is " + bas.colbasisstatus[i]);
       }
+       // Add a Hessian
+      int dim = 2;
+      int[] qstart = {0, 2};
+      int[] qindex = {0, 1, 1};
+      double[] qvalue = {2, -1, 2};
+      HessianFormat q_format = HessianFormat.kTriangular;
+
+
    }
-}
+}

src/interfaces/highs_csharp_api.cs

@@ -113,6 +113,7 @@ public HighsModel(double[] colcost, double[] collower, double[] colupper, double
 public class HighsHessian
 {
     public HessianFormat q_format;
+    public int dim;
     public int[] qstart;
     public int[] qindex;
     public double[] qvalue;
@@ -122,8 +123,9 @@ public HighsHessian()
 
     }
 
-    public HighsHessian(int[] qstart, int[] qindex, double[] qvalue, HessianFormat q_format = HessianFormat.kTriangular)
+    public HighsHessian(int dim, int[] qstart, int[] qindex, double[] qvalue, HessianFormat q_format = HessianFormat.kTriangular)
     {
+        this.dim = dim;
         this.qstart = qstart;
         this.qindex = qindex;
         this.qvalue = qvalue;
@@ -721,6 +723,18 @@ public HighsStatus passMip(HighsModel model)
             model.highs_integrality);
     }
 
+    public HighsStatus passHessian(HighsHessian hessian)
+    {
+        return (HighsStatus)HighsLpSolver.Highs_passHessian(
+            this.highs,
+            hessian.dim,
+            hessian.qvalue.Length,
+            (int)hessian.q_format,
+            hessian.qstart,
+            hessian.qindex,
+            hessian.qvalue);
+    }
+
     public HighsStatus setOptionValue(string option, string value)
     {
         return (HighsStatus)HighsLpSolver.Highs_setOptionValue(this.highs, option, value);