diff --git a/SunnyUI.Demo.sln b/SunnyUI.Demo.sln
index df4086ba..2faa5748 100644
--- a/SunnyUI.Demo.sln
+++ b/SunnyUI.Demo.sln
@@ -1,5 +1,5 @@
 
-Microsoft Visual Studio Solution File, Format Version 12.00
+Microsoft Visual Studio Solution File, Format Version 11.00
 # Visual Studio 2010
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SunnyUI.Demo", "SunnyUI.Demo\SunnyUI.Demo.csproj", "{6AE19B87-C2AA-4C56-BC26-1C343F30FF58}"
 EndProject
diff --git a/SunnyUI.Demo/Bin/SunnyUI.Demo.exe b/SunnyUI.Demo/Bin/SunnyUI.Demo.exe
index 4a89066a..776234ca 100644
Binary files a/SunnyUI.Demo/Bin/SunnyUI.Demo.exe and b/SunnyUI.Demo/Bin/SunnyUI.Demo.exe differ
diff --git a/SunnyUI.Demo/Controls/FCombobox.cs b/SunnyUI.Demo/Controls/FCombobox.cs
index aa614d4b..34b20cef 100644
--- a/SunnyUI.Demo/Controls/FCombobox.cs
+++ b/SunnyUI.Demo/Controls/FCombobox.cs
@@ -113,21 +113,11 @@ namespace Sunny.UI.Demo
 
         private void uiComboDataGridView1_ValueChanged(object sender, object value)
         {
-            if (value == null)
+            uiComboDataGridView1.Text = "";
+            if (value != null && value is DataGridViewRow)
             {
-                uiComboDataGridView1.Text = "";
-            }
-            else
-            {
-                if (value is DataGridViewRow)
-                {
-                    DataGridViewRow row = (DataGridViewRow)value;
-                    uiComboDataGridView1.Text = row.Cells["Column1"].Value.ToString();
-                }
-                else
-                {
-                    uiComboDataGridView1.Text = "";
-                }
+                DataGridViewRow row = (DataGridViewRow)value;
+                uiComboDataGridView1.Text = row.Cells["Column1"].Value.ToString();
             }
         }
 
@@ -158,21 +148,15 @@ namespace Sunny.UI.Demo
 
         private void uiComboDataGridView2_ValueChanged(object sender, object value)
         {
-            if (value == null)
+            uiComboDataGridView2.Text = "";
+            if (value != null && value is DataGridViewSelectedRowCollection)
             {
-                uiComboDataGridView2.Text = "";
-            }
-            else
-            {
-                uiComboDataGridView2.Text = "";
-                if (value is DataGridViewSelectedRowCollection collection)
+                DataGridViewSelectedRowCollection collection = (DataGridViewSelectedRowCollection)value;
+                foreach (var item in collection)
                 {
-                    foreach (var item in collection)
-                    {
-                        DataGridViewRow row = (DataGridViewRow)item;
-                        uiComboDataGridView2.Text += row.Cells["Column1"].Value.ToString();
-                        uiComboDataGridView2.Text += "; ";
-                    }
+                    DataGridViewRow row = (DataGridViewRow)item;
+                    uiComboDataGridView2.Text += row.Cells["Column1"].Value.ToString();
+                    uiComboDataGridView2.Text += "; ";
                 }
             }
         }
diff --git a/SunnyUI.Demo/SunnyUI.Demo.csproj b/SunnyUI.Demo/SunnyUI.Demo.csproj
index 3bc99785..992a0267 100644
--- a/SunnyUI.Demo/SunnyUI.Demo.csproj
+++ b/SunnyUI.Demo/SunnyUI.Demo.csproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>