Avoid throwing in ToString() if the process has already exited

src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.cs

@@ -1361,15 +1361,31 @@ private void StopWatchingForExit()
 
         public override string ToString()
         {
-            if (Associated)
+            string result = base.ToString();
+
+            try
             {
-                string processName = ProcessName;
-                if (processName.Length != 0)
+                if (Associated)
                 {
-                    return $"{base.ToString()} ({processName})";
+                    _processInfo ??= ProcessManager.GetProcessInfo(_processId, _machineName);
+                    if (_processInfo is not null)
+                    {
+                        string processName = _processInfo.ProcessName;
+                        if (processName.Length != 0)
+                        {
+                            result = $"{result} ({processName})";
+                        }
+                    }
                 }
             }
-            return base.ToString();
+            catch
+            {
+                // Common contract for ToString methods is never throw.
+                // Handle cases where a process would terminates immediately after our checks
+                // and/or cause ProcessManager to throw an exception.
+            }
+
+            return result;
         }
 
         /// <devdoc>

src/libraries/System.Diagnostics.Process/tests/ProcessTests.cs

@@ -467,6 +467,27 @@ public void TestHasExited()
             }
         }
 
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void TestToString_OnRunningProcess()
+        {
+            Process p = CreateDefaultProcess();
+            var name = p.ProcessName;
+            Assert.Equal($"System.Diagnostics.Process ({name})", p.ToString());
+
+            KillWait(p);
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void TestToString_OnExitedProcess()
+        {
+            Process p = CreateDefaultProcess();
+            KillWait(p);
+
+            // Ensure ToString does not throw an exception, but still returns
+            // a representation of the object.
+            Assert.Equal("System.Diagnostics.Process", p.ToString());
+        }
+
         [Fact]
         public void HasExited_GetNotStarted_ThrowsInvalidOperationException()
         {