本文整理汇总了C#中System.Data.Common.DbProviderFactory.ExecuteScalar方法的典型用法代码示例。如果您正苦于以下问题：C# DbProviderFactory.ExecuteScalar方法的具体用法？C# DbProviderFactory.ExecuteScalar怎么用？C# DbProviderFactory.ExecuteScalar使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类System.Data.Common.DbProviderFactory的用法示例。
在下文中一共展示了DbProviderFactory.ExecuteScalar方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的C#代码示例。
示例1: _DatabaseExists
private static bool _DatabaseExists(DbProviderFactory provider, string connectionString, string providerName)
{
string dbName, cmdText = null;
string connStr = _StripDbName(connectionString, providerName, out dbName);
try
{
log.DebugFormat(
CultureInfo.InvariantCulture,
"Checking if database '{0}' exists, with provider: {1}, and connectionString: {2}",
dbName,
providerName,
connStr);
if (providerName == SQLiteProvider)
{
if (dbName.ToUpperInvariant() == ":MEMORY:")
{
return false;
}
else
{
return File.Exists(dbName);
}
}
if (providerName == SqlCe || providerName == Firebird)
{
return File.Exists(dbName);
}
switch (providerName)
{
case MsSqlProvider:
cmdText = string.Format(CultureInfo.InvariantCulture, "select COUNT(*) from sys.sysdatabases where name=\'{0}\'", dbName);
break;
case MySqlProvider:
cmdText = string.Format(
CultureInfo.InvariantCulture,
@"SELECT COUNT(*) FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = '{0}'",
dbName);
break;
case OracleDataProvider:
cmdText = "SELECT 1 FROM DUAL";
break;
case PostgreSQLProvider:
cmdText = string.Format(
CultureInfo.InvariantCulture,
"select count(*) from pg_catalog.pg_database where datname = '{0}'",
dbName);
break;
default:
throw new NotSupportedException(string.Format(
CultureInfo.InvariantCulture,
"Provider {0} is not supported",
providerName));
}
object ret = provider.ExecuteScalar(connStr, cmdText);
int count = ret == null ? 0 : Convert.ToInt32(ret, CultureInfo.InvariantCulture);
if (count > 0)
{
return true;
}
}
catch (NotSupportedException)
{
throw;
}
catch (Exception ex)
{
log.Error("Database connection failed", ex);
}
log.DebugFormat(CultureInfo.InvariantCulture, "Database '{0}' does not exists", dbName);
return false;
}