variable to pass to 'typeof' operator in asp.net

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ASP.NET

In the belwo code i want to generalize 'typeof' that's why i have designed to pass parameter 'typ' to 'typeof' operator . I don't have the idea of 'typ' variable but it's not working !!! So, how i can generalized the variable to be passed to 'typeof' operator and what is it's variable type !!!! My code :

public static string BuildWhereCondition(Type typ, string columnName, string columnValue)
{
    string whereCondition = string.Empty;
    PropertyInfo columnInfo = typeof(typ).GetProperty(columnName);
    if (columnInfo != null)
    {
       if (columnInfo.PropertyType == typeof(int))
       {
           whereCondition = columnName + "=" + columnValue;
       }
       else if (columnInfo.PropertyType == typeof(String))
       {
           whereCondition = columnName + " LIKE '%" + columnValue + "%'";
       }
       else if (columnInfo.PropertyType == typeof(DateTime))
       {
           whereCondition = columnName + "='" + columnValue + "'";
       }
    }
    return whereCondition;
}

Thanks in advance .