Add CSharpFormattingOptions.IndentationString

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpFormattingOptions.cs

@@ -86,6 +86,8 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 		}
 
 		#region Indentation
+		public string IndentationString { get; set; } = "\t";
+
 		public bool IndentNamespaceBody { // tested
 			get;
 			set;

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -45,7 +45,7 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			if (formattingPolicy == null) {
 				throw new ArgumentNullException ("formattingPolicy");
 			}
-			this.writer = TokenWriter.Create(textWriter);
+			this.writer = TokenWriter.Create(textWriter, formattingPolicy.IndentationString);
 			this.policy = formattingPolicy;
 		}
 		

ILSpy/TextView/AvalonEditTextOutput.cs

@@ -76,6 +76,8 @@ namespace ICSharpCode.ILSpy.TextView
 		int indent;
 		/// <summary>Whether indentation should be inserted on the next write</summary>
 		bool needsIndent;
+
+		public string IndentationString { get; set; } = "\t";
 		
 		internal readonly List<VisualLineElementGenerator> elementGenerators = new List<VisualLineElementGenerator>();
 		
@@ -176,7 +178,7 @@ namespace ICSharpCode.ILSpy.TextView
 			if (needsIndent) {
 				needsIndent = false;
 				for (int i = 0; i < indent; i++) {
-					b.Append('\t');
+					b.Append(IndentationString);
 				}
 			}
 		}