1 files changed, 36 insertions, 0 deletions
diff --git a/src/ProtoGen/InvalidOptionsException.cs b/src/ProtoGen/InvalidOptionsException.cs
new file mode 100644
index 00000000..aee03228
--- /dev/null
+++ b/src/ProtoGen/InvalidOptionsException.cs
@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Google.ProtocolBuffers.Collections;
+
+namespace Google.ProtocolBuffers.ProtoGen {
+  /// <summary>
+  /// Exception thrown to indicate that the options passed were invalid.
+  /// </summary>
+  public sealed class InvalidOptionsException : Exception {
+
+    private readonly IList<string> reasons;
+
+    /// <summary>
+    /// An immutable list of reasons why the options were invalid.
+    /// </summary>
+    public IList<string> Reasons {
+      get { return reasons; }
+    }
+
+    public InvalidOptionsException(IList<string> reasons) 
+        : base(BuildMessage(reasons)) {
+      this.reasons = Lists.AsReadOnly(reasons);
+    }
+
+    private static string BuildMessage(IEnumerable<string> reasons) {
+      StringBuilder builder = new StringBuilder("Invalid options:");
+      builder.AppendLine();
+      foreach (string reason in reasons) {
+        builder.Append("  ");
+        builder.AppendLine(reason);
+      }
+      return builder.ToString();
+    }
+  }
+}