Database

public void UpdateDashboardInfo(AssayDashboardInfoEntity entity)
{
    try
    {
        using (var context = new AssayDashboardDataContext())
        {
            AssayDashboardInfo model = null;

            try
            {
                model = (from adi
                            in context.AssayDashboardInfos
                            where adi.ResultId.CompareTo(entity.ResultId) > 0
                            select adi).FirstOrDefault();                     // <= EXCEPTION HERE
            }
            catch (Exception e1)
            {
                _logger.Error("****** ARD_DAL: UpdateDashboardInfo (Query)", e1);
            }

            if (model != null)
            {
                model.SiteId = entity.SiteId;
                model.InstrumentId = entity.InstrumentId;
                model.TowerLocation = entity.TowerLocation;

                context.SubmitChanges();
            }
        }
    }
    catch (Exception e)
    {
        _logger.Error("********** ARD_DAL: UpdateDashboardInfo", e);
    }
}

declare cur cursor for Select Table_Name From INFORMATION_SCHEMA.COLUMNS Where column_name = 'INV_DATE'
declare @tablename nvarchar(max)
declare @sqlstring nvarchar(max)
open cur
fetch next from cur into @tablename
while @@fetch_status=0
begin
--print @tablename

set @sqlstring = 'update '+@tablename+' SET INV_DATE = CONVERT(varchar(10),INV_DATE,105)'

exec sp_executesql @sqlstring

fetch next from cur into @tablename
end

close cur
deallocate cur

Please suggest me a solution 

current format:2016-03-31 00:00:00.000
Required Format:31-03-2016
DataType:DateTime

I tried to copy data and changing to DateTime using temp field.But also getting the same error.

<pre lang="SQL">alter table GL add GL_DATE1 datetime null
update GL set GL_DATE=convert(datetime,GL_DATE,104)-------->Getting error here
update GL set GL_DATE1=GL_DATE
alter table GL drop column GL_DATE
SP_RENAME 'GL.GL_DATE1','GL_DATE','column'

1. create object "SqlConnection" and let connection opened during service (webservice) works
2. using the instruction below every time I want to do a modification in dtatabase

 using (SqlConnection sqlconnection = GetSqlConnection(connectionString, false))
                {
                    sqlconnection.Open();
.....

}

public static SqlConnection GetSqlConnection(string connectionString, bool disablePooling = true, bool forceMasterDB = false)
       {
           if (disablePooling || forceMasterDB)
           {
               SqlConnectionStringBuilder sqlConnBuilder = new SqlConnectionStringBuilder(connectionString);

               if (disablePooling)
                   sqlConnBuilder.Pooling = false;

               if (forceMasterDB)
                   sqlConnBuilder.InitialCatalog = "master";

               connectionString = sqlConnBuilder.ConnectionString;
           }
           return new SqlConnection(connectionString);
       }