diff --git a/Src/Asp.NetCore2/SqlSugar/Abstract/QueryableProvider/MappingFieldsHelper.cs b/Src/Asp.NetCore2/SqlSugar/Abstract/QueryableProvider/MappingFieldsHelper.cs
index 2263ff724..5fed9d2c1 100644
--- a/Src/Asp.NetCore2/SqlSugar/Abstract/QueryableProvider/MappingFieldsHelper.cs
+++ b/Src/Asp.NetCore2/SqlSugar/Abstract/QueryableProvider/MappingFieldsHelper.cs
@@ -44,7 +44,7 @@ namespace SqlSugar
                         FieldName = item.LeftEntityColumn.DbColumnName,
                         ConditionalType = ConditionalType.Equal,
                         FieldValue = item.RightEntityColumn.PropertyInfo.GetValue(model).ObjToString(),
-                        CSharpTypeName = item.RightEntityColumn.PropertyInfo.PropertyType.Name
+                        CSharpTypeName =UtilMethods.GetUnderType(item.RightEntityColumn.PropertyInfo.PropertyType).Name
                     }));
                     i++;
                 }
diff --git a/Src/Asp.NetCore2/SqlSugar/Utilities/UtilMethods.cs b/Src/Asp.NetCore2/SqlSugar/Utilities/UtilMethods.cs
index 6063ff3d6..f53344a61 100644
--- a/Src/Asp.NetCore2/SqlSugar/Utilities/UtilMethods.cs
+++ b/Src/Asp.NetCore2/SqlSugar/Utilities/UtilMethods.cs
@@ -782,6 +782,10 @@ namespace SqlSugar
                 CSharpTypeName = ctypename,
                 FieldValue = value
             };
+            if (item.FieldValue == string.Empty && item.CSharpTypeName.HasValue() && !item.CSharpTypeName.EqualCase("string")) 
+            {
+                return null;
+            }
             if (item.CSharpTypeName.EqualCase(UtilConstants.DecType.Name))
             {
                 return Convert.ToDecimal(item.FieldValue);