Set `DatabaseExists` before closing.

framework/src/Volo.Abp.EntityFrameworkCore.MySQL/Volo/Abp/EntityFrameworkCore/ConnectionStrings/AbpEfCoreMySqlConnectionStringChecker.cs

@@ -25,8 +25,10 @@ public class AbpEfCoreMySqlConnectionStringChecker : IAbpConnectionStringChecker
             await conn.OpenAsync();
             result.Connected = true;
             await conn.ChangeDatabaseAsync(oldDatabaseName);
-            await conn.CloseAsync();
             result.DatabaseExists = true;
+
+            await conn.CloseAsync();
+
             return result;
         }
         catch (Exception e)

framework/src/Volo.Abp.EntityFrameworkCore.SqlServer/Volo/Abp/EntityFrameworkCore/ConnectionStrings/AbpEfCoreSqlServerConnectionStringChecker.cs

@@ -25,8 +25,10 @@ public class AbpEfCoreSqlServerConnectionStringChecker : IAbpConnectionStringChe
             await conn.OpenAsync();
             result.Connected = true;
             await conn.ChangeDatabaseAsync(oldDatabaseName);
-            await conn.CloseAsync();
             result.DatabaseExists = true;
+
+            await conn.CloseAsync();
+
             return result;
         }
         catch (Exception e)

framework/src/Volo.Abp.EntityFrameworkCore.Sqlite/Volo/Abp/EntityFrameworkCore/ConnectionStrings/AbpEfCoreSqliteConnectionStringChecker.cs

@@ -18,6 +18,7 @@ public class AbpEfCoreSqliteConnectionStringChecker : IAbpConnectionStringChecke
             await conn.OpenAsync();
             result.Connected = true;
             result.DatabaseExists = true;
+
             await conn.CloseAsync();
 
             return result;